S9Q1W4-5 | Non-Mendelian Inheritance

Summary

This video lesson for grade nine science focuses on non-Mendelian inheritance, exploring genetic variations beyond traditional Mendelian patterns. It defines key terms like genetics, inheritance, gene, genotype, and phenotype, and differentiates between them. The lesson delves into non-Mendelian inheritance types: incomplete dominance, co-dominance, and multiple alleles, using examples like flower colors and blood types. It also covers sex-linked inheritance, explaining how traits like baldness are passed down through X chromosomes. The use of Punnett squares to predict genetic outcomes is highlighted, with activities to engage students in applying these concepts.

Takeaways

• 🌟 Genetics is a branch of biology that studies genes, genetic variation, and heredity in organisms.
• 🔬 Inheritance is the process by which genetic information is passed from parents to offspring.
• 🧬 A gene is a unit of heredity, a section of DNA that codes for a specific trait.
• 🌺 Genotype refers to the genetic makeup of an organism, which is the combination of two alleles.
• 🌻 Phenotype is the physical appearance or trait of an organism, such as the color of a flower.
• 🎯 Homozygous means having two identical alleles, while heterozygous means having two different alleles.
• 📊 Punnett Square is a tool used to predict the genotypes of offspring from a particular cross or breeding event.
• 👨‍🔬 Gregor Mendel is known as the father of genetics for his foundational work on inheritance patterns.
• 🚫 Non-Mendelian inheritance occurs when genetic patterns do not follow Mendel's laws.
• 🌹 Incomplete dominance is a type of inheritance where one allele does not completely dominate another, resulting in a new phenotype.
• 🤝 Co-dominance is a type of inheritance where both alleles are expressed equally in the phenotype of the heterozygote.

Q & A

What is the focus of the lesson for grade nine science in week four to five?

The focus of the lesson is to describe the location of genes in chromosomes and explain different patterns of non-Mendelian inheritance.

What is genetics and how does it relate to the study of inheritance?

Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. It relates to the study of inheritance as it deals with how genetic information is passed on from parents to offspring.

What is the difference between genotype and phenotype as explained in the lesson?

Genotype refers to the genetic makeup of an organism, which is the combination of two alleles. Phenotype, on the other hand, is the physical appearance or trait of an organism, which is the expression of the genotype.

Can you explain the concept of homozygous and heterozygous in the context of genetics?

Homozygous refers to having two identical alleles for a particular gene, while heterozygous means having two different alleles for that gene.

What is a Punnett square and how is it used in genetics?

A Punnett square is a graphical representation used to predict the possible genotypes of offspring from a particular cross or breeding event. It helps visualize the combination of alleles from each parent.

Who is Gregor Mendel and why is he significant in the field of genetics?

Gregor Mendel is considered the father of genetics. He began a decade-long research project to investigate patterns of inheritance, studying the inheritance of seven different traits in pea plants, and his principles form the basis for understanding heredity and variation.

What is non-Mendelian inheritance and how does it differ from Mendelian inheritance?

Non-Mendelian inheritance refers to patterns of inheritance where the traits do not follow Mendel's laws. This can occur in cases such as incomplete dominance, co-dominance, and multiple alleles, where the expression of traits is not simply dominant or recessive.

What is incomplete dominance and how is it demonstrated in the lesson?

Incomplete dominance is a form of inheritance where one allele does not completely dominate another, resulting in a new or third phenotype. In the lesson, this is demonstrated by crossing red and white snapdragon flowers, resulting in pink flowers.

What is co-dominance and how is it different from incomplete dominance?

Co-dominance is a type of inheritance where both alleles are expressed equally in the phenotype of the heterozygote. It is different from incomplete dominance in that both traits are visible in the offspring, rather than a blend of the two.

What are multiple alleles and provide an example from the lesson?

Multiple alleles occur when a gene is controlled by more than two alleles. An example from the lesson is blood types, where there are four possible blood types (A, B, AB, and O), each controlled by different combinations of alleles.

How is sex determination and inheritance explained in the lesson?

Sex determination and inheritance are explained through the understanding that humans have 23 pairs of chromosomes, with the 23rd pair being sex chromosomes. Males have XY and females have XX chromosomes. The sex of a child is determined by the chromosome contributed by the father's sperm (X for female, Y for male).

What are sex-linked traits and how do they differ from other types of inheritance?

Sex-linked traits are inherited through the X chromosomes and are more common in males because they have only one X chromosome. Females have two X chromosomes, so they can be carriers without expressing the trait. This differs from autosomal inheritance, where traits are inherited through any of the non-sex chromosomes.

Outlines

00:00

🧬 Genetics and Non-Mendelian Inheritance

This paragraph introduces the topic of non-Mendelian inheritance in grade nine science. It explains the basics of genetics, including the concepts of inheritance, variation, genes, genotype, and phenotype. The lesson aims to help students describe the location of genes in chromosomes and understand different patterns of non-Mendelian inheritance. Examples are given to differentiate between genotype and phenotype using the four o'clock flower. The paragraph also covers the terms homozygous and heterozygous, and introduces Punnett squares and Gregor Mendel's contributions to genetics. Non-Mendelian inheritance is presented as a deviation from Mendelian patterns, with incomplete dominance being the first type discussed, exemplified by the red and white snapdragon flowers resulting in a pink offspring.

05:01

🌺 Incomplete and Co-Dominance Inheritance

This section delves into the concept of incomplete dominance in genetics, where one allele does not fully dominate another, leading to a new phenotype. The example of red and white snapdragon flowers crossing to produce pink flowers is used to illustrate this point. The process is demonstrated using a Punnett square to show the genotypes and phenotypes resulting from the cross. Co-dominance is introduced as a type of inheritance where both alleles are expressed equally in the phenotype. Examples include red and white flowers crossing to produce red and white flowers, and the activity where students distinguish between incomplete dominance and co-dominance in various scenarios.

10:02

🩸 Multiple Alleles and Blood Types

The paragraph discusses the third type of non-Mendelian inheritance, which is multiple alleles. This occurs when a gene is controlled by more than two alleles. Blood type is used as a prime example, with four blood types (A, B, AB, and O) explained in terms of their antigens and genotypes. The universal donor and receiver concepts are introduced with blood type O and AB, respectively. A problem-solving scenario is presented where a couple with blood type A must identify their son among two babies with unknown parents, one with blood type B and the other with blood type O. Students are guided to solve this using Punnett squares for different trial scenarios.

15:04

🧍‍♂️ Sex Determination and Sex-Linked Traits

This part of the script covers sex determination and inheritance, explaining the role of the 23rd pair of chromosomes, which are the sex chromosomes. It details how males have XY and females have XX chromosomes, and how these determine the baby's sex. The paragraph introduces three types of sex-related inheritance: sex-linked traits (inherited through the X chromosome), sex-influence traits (expressed differently in males and females with the same genotype), and sex-limited traits (expressed in only one sex). An example of a sex-linked trait, pattern baldness, is used to illustrate how this trait is inherited and can affect males and females differently.

20:05

📚 Problem Solving with Punnett Squares

The final paragraph focuses on applying the knowledge of genetics to solve a problem involving sex-linked traits using Punnett squares. Students are tasked with determining the possible genotypes and phenotypes of offspring from a cross between a male with a disorder and a female carrier of the disorder. The paragraph provides a step-by-step guide on how to use a Punnett square for this purpose. The lesson concludes with instructions for students to complete their assignments, either by writing answers on paper or submitting photos of their work through Google Classroom.

Keywords

💡Genetics

Genetics is a branch of biology that studies genes, genetic variation, and heredity in organisms. In the video, genetics is the central theme as it discusses how genetic information is passed from parents to offspring and how traits are inherited. The script uses genetics to explain various patterns of inheritance and the role of genes in determining an organism's characteristics.

💡Inheritance

Inheritance refers to the process by which genetic information is passed on from parents to their offspring. The video script delves into different patterns of inheritance, including Mendelian and non-Mendelian, to explain how traits are transmitted across generations. It is a fundamental concept in understanding the genetic makeup of organisms.

💡Variation

Variation in biology denotes the differences between cells, individual organisms, or groups of organisms within any species. The video lesson discusses variation in the context of genetic diversity, which is crucial for evolution and the survival of species. It is highlighted as a key aspect that genetics helps to explain.

💡Gene

A gene is defined as a unit of heredity, a section of DNA that codes for a specific trait. In the video, genes are discussed in relation to their location on chromosomes and their role in determining an organism's phenotype. The script uses examples like the four o'clock flower to illustrate how different gene combinations (genotypes) result in different physical appearances (phenotypes).

💡Genotype

Genotype is the genetic makeup of an organism, referring to the combination of two alleles. The video script differentiates between genotype and phenotype, using the example of the four o'clock flower to show that while the genotype (fr fr or fw fw) determines the genetic composition, it is the phenotype that is observable.

💡Phenotype

Phenotype refers to the physical appearance or the physical feature of an organism, which is the expression of its genotype. The video explains that while the genotype is the underlying genetic code, the phenotype is what is observed, such as the color of a flower. Phenotypes are influenced by both genotype and environmental factors.

💡Homozygous

Homozygous means having two identical alleles for a particular gene. In the context of the video, homozygous organisms are used to illustrate how certain traits are consistently expressed when both alleles are the same. This concept is important for understanding how traits are passed down without variation in offspring.

💡Heterozygous

Heterozygous refers to having two different alleles for a particular gene. The video script uses heterozygous genotypes to explain how traits can be mixed or blended in offspring, leading to different expressions than either parent. This is a key concept in understanding genetic diversity and variation.

💡Punnett Square

A Punnett Square is a graphical representation used to predict the genotypes and phenotypes of offspring resulting from a particular cross or breeding event. The video script demonstrates how to use a Punnett Square to predict outcomes of genetic crosses, such as the example of red and white snapdragon flowers, which is crucial for understanding inheritance patterns.

💡Non-Mendelian Inheritance

Non-Mendelian inheritance refers to patterns of inheritance that do not follow Mendel's laws, such as those involving genes on the same chromosome that are inherited together. The video discusses three types of non-Mendelian inheritance: incomplete dominance, co-dominance, and multiple alleles. These concepts are important for understanding the complexity of genetic inheritance beyond simple Mendelian patterns.

💡Sex-Linked Inheritance

Sex-linked inheritance involves genes located on the sex chromosomes, which can result in different inheritance patterns depending on an individual's sex. The video script explains how traits like pattern baldness can be inherited differently in males and females due to the presence of the gene on the X chromosome. This concept is crucial for understanding how certain genetic conditions are more prevalent in one sex over another.

Highlights

Introduction to non-Mendelian inheritance in grade nine science.

Explanation of genetic terms like genetics, inheritance, variation, gene, genotype, and phenotype.

Differentiation between genotype and phenotype using the example of a four o'clock flower.

Definition of homozygous and heterozygous alleles.

Introduction to Punnett Square and its use in predicting genetic outcomes.

Historical context of Gregor Mendel's work and his significance in genetics.

Concept of non-Mendelian inheritance and its deviation from Mendelian laws.

Description of incomplete dominance and its outcome using red and white snapdragon flowers.

Demonstration of incomplete dominance using a Punnett Square with snapdragon flowers.

Explanation of co-dominance and its example with red and white flowers.

Activity to distinguish between incomplete dominance and co-dominance with various examples.

Introduction to multiple alleles and its example with blood types.

Detailed explanation of blood types and their corresponding antigens and genotypes.

Practical problem-solving using Punnett Square to identify a couple's son among two babies with different blood types.

Discussion on sex-related inheritance and the role of sex chromosomes in determining gender.

Explanation of sex-linked traits, sex-influence traits, and sex-limited traits.

Example of sex-linked inheritance with pattern baldness and its genetic implications.

Problem-solving activity involving Punnett Square to predict genotypes and phenotypes in sex-linked traits.

Summary of the lesson on non-Mendelian patterns of inheritance and sex-related inheritance.

Transcripts

today's video lesson we are going to

discuss grade nine science quarter one

module one week four to five

non-mendelian inheritance to better

understand this pattern please keep on

watching

you learned that cells divide to produce

new cells and meiosis is one of the

processes producing genetic variations

in mendelian patterns of inheritance

today in grade nine science you will

focus on describing the location of

genes in chromosomes and explain the

different patterns of non-mendelian

inheritance so without further ado let's

get started

before we proceed

let us start with unlocking of

difficulties

these are the terms that you will

encounter all throughout the lesson so

let us define them and be familiar with

this

first term

it is a branch of biology concerned with

the study of genes

genetic variation and heredity in

organism this is

genetics that's right

the next term

a process by which genetic information

is passed on

from parents to child that is inheritan

any difference between cells

individual organisms or groups of

organism of any species that is

variation

next

a unit of heredity a section of dna that

codes for a specific trait that is our

gene

next

i know that you are all familiar with

genotype and phenotype now let us

differentiate them first up genotype it

is the genetic makeup of organism it is

the combination of two alleles

well the phenotype is the physical

appearance or the physical feature or

the trait of an organism let's have an

example of genotype and phenotype

four o'clock flower so i have here two

flowers as you can see

what is the genotype of the first flower

the genotype is fr fr the combination of

two alleles how about the other one

that is

fwfw

that is the genotype the genetic makeup

of organisms well the phenotype

the phenotype of the first one is

red because it is color red it is its

appearance and the other one is

white the physical appearance or the

feature or the trait of the organism

that is the difference between the

genotype and the phenotype is that clear

class

now let us proceed

let us define homozygous it means having

two identical alleles and heterozygous

means having two different alleles

next up

i know that you already know how to use

punnett square pilot square is a

graphical representation of the possible

genotypes of an offspring arising from a

particular cross or breathing event

reginald bonnet is the proponent of

bonnet square

next the you know gregor

mandel gregor mendel began a decade-long

research project to investigate patterns

of inheritance he studied the

inheritance of seven different features

in peace including the height flower

color seed color and seed shape gregor

mendel's principles form the base for

the understanding of heredity and

variation that is why he is considered

the father of genetics

next

non-mendelian inheritance this is a type

of inheritance where in the patterns of

tina times does not coincide with those

that was presented in the mendelian law

of inheritance and this is our lesson

for today

the three types of non-mendelian

inheritance let's have the first type

that is incomplete dominance it is a

form of intermediate inheritance in

which one allele does not completely

dominate another allele

resulting in a new or a third phenotype

let's have an example of incomplete

dominance we have here

a red snapdragon flower

cross to a white snapdragon flower and

the result is

a pink snapdragon flower one allele does

not completely dominate another allele

resulting in a third or new phenotype

and that is

the pink snapdragon flower

now let me show you how it happened

using the planet square

as you can see our genotype for red

snapdragon flower is frfr

our genotype for white snapdragon flower

is fwfw

let us cross using punnett square

so this is our genotype let us cross it

downward

and then sideward

so these are the results

now let us identify the genotypes always

remember each box is equal to 25 percent

so as you can see

they are all the same all the genotypes

are the same f r f w

therefore

100 percent the genotypes are f r f w

the phenotype is the physical appearance

now the result when we cross

red snapdragon flower and white

snapdragon flower is 100

pink snapdragon flower that is how we

use spawnet square

let's have another example

show the possible outcome of the cross

between white flower

and pink flower

so what are our genotypes for a white

flower our genotypes are fw and fw

for pink flower

our genotypes are fr and fw

not fp and fb that is wrong because a

pink flower originated from the red and

white flower that is why the genotypes

are fr and fw

always remember that now let us cross fw

or the white flower and the pink flower

using punnett square

downward and then

sideward

so here it is as you can see

we have here

two f r f w and two f w f w now let us

determine the genotypes and the

phenotypes the genotypes are fifty

percent frfw 50

fw fw how about the phenotypes what is

the meaning of frfw that is pink flower

therefore we have 50

pink flower how about fwfw it means

white flower that is why our phenotypes

are 50

white flower and 50

pink flower

understood glass

now let us proceed to the second type of

non-mendelian inheritance and that is

what we called cod dominance

codabenance means both alleles are

expressed equally in the phenotype of

the heterozygote

for example red flower plus white flower

the result is

red and white flower as you can see in

codominance both alleles both appearance

or both traits are expressed equally red

and white that is called dominance let

us have an example

let us cross red and white flower

so here it is as you can see in using

punnett square

100

red and white flower

now let us have an activity

i will be showing pictures and you are

going to distinguish if it is incomplete

dominance or

co-dominance let's get started

first one

standard pudel plus labrador equals

labradoodle

what is this is this incomplete

dominance or co-dominance

this is incomplete dominance because one

allele does not completely dominate

another allele resulting to

a new phenotype that's right next we

have here white chicken mated to black

chicken the result is checkered chicken

as you can see

what is this type of inheritance this is

what we called

that's right cod dominance because both

alleles are expressed equally as you can

see in the chicken it has white and

black

next

orange fur cut and block per cut

what do you think is the result

orange and black fur cut

and this is an example of

cod dominance that is right because both

alleles are expressed equally okay next

one

we have here straight hair

and a curly hair

what do you think will be the result

we have

wavy hair and this is an example of

incomplete dominance because we have a

third phenotype or a new phenotype which

is wavy hair okay good job i know that

you already know the difference between

incomplete dominance and cod dominance

now let us proceed to the third type of

non-mendelian pattern of inheritance and

that is what we call multiple alleles

from the word itself

multiple it is a gene that is controlled

by more than two alleles and one good

example of multiple alleles

is our blood type

do you know your blood type class it is

important that we know our blood type

okay so we have four blood types we have

blood type a

blood type b

blood type a b and blood type o

so which blood type do you have

these are the four blood types blood

type a has antigen a

blood type b has antigen b blood type a

b has antigen a and b

and blood type o

has no antigen or neither antigen a nor

antigen b

next

so these are the genotype of blood types

for blood type a as you can see we have

two genotypes we have the homozygous ia

and the heterozygous ia small eye

blood type a can receive blood from

itself blood type a and blood type o

blood type b

we also have two genotypes

homozygous and heterozygous

blood type b can receive blood from

blood type b and blood type o

for blood type a b it is an example of

both codominance

and a trait with multiple alleles it has

a genotype of ia and ib it can receive

blood from blood type a blood type b

blood type a b and blood type o that is

why it is called the universal blood

receiver

blood type o has a genotype of small eye

small eye because it has no antigen it

can receive blood from blood type o only

and as you can see

blood type o can donate blood to any

type of blood type because it is

considered the universal donor

now let us have a problem

a couple gives birth to a baby boy

both parents have blood type a

however

there is a confusion in the hospital

there are two babies which have unknown

parents

the first baby has blood type b

while the second baby has blood type o

help the couple find their son so for

this problem you are going to answer

this on your paper

you will construct a punnett square to

solve this problem

for blood type a we have two kinds of

genotype the homozygous and the

heterozygous according to the problem

there is no specific detail that the

parents are homozygous or heterozygous

that is why we are going to do a trial

and error

trial number one

both parents have homozygous blood type

a you will cross this using pune square

for trial two

one parent is homozygous and the other

one is heterozygous

for trial 3

both of them are heterozygous let us see

which one is their real bp

these are the guide questions list down

the genotypes and the phenotypes for

each trial

and for question number two who is the

real son of the couple

for mdl students write your answers on

your paper and for odl students write

your answers on a piece of paper and

take a picture and attach it to the

respective assignment in your science

google classroom so do not forget to

screenshot the problem and the guide

questions and solve this on a piece of

paper

answer very well class

so those are the three types of

non-mendelian pattern of inheritance

which are incomplete dominance cod

dominance and multiple alleles now let

us proceed to the next one some traits

are controlled by sex-related

inheritance now let us have the sex

chromosomes and sex determination

in each cell

humans have 46 chromosomes or a total of

23 pairs of chromosomes from our parents

22 pairs of those are what we call the

somatic chromosomes that contains all

our genetic information or all the

traits that we inherit from our parents

the 23rd pair consists of our sex

chromosomes or our gametes that

determines our gender

the male chromosomes are

x y they are the non-identical sex

chromosomes the female chromosomes are x

and x they are identical sex chromosomes

always remember

female have x and x chromosome and male

have

x and y chromosomes

how is sex determined and inherited

when an egg is fertilized by a sperm

carrying a y chromosome the baby will be

male

when an egg is fertilized by a sperm

carrying an x chromosome the baby will

be

female therefore

the sex chromosomes that determine the

person's gender or the baby's gender

will be the chromosomes of the father

what percent of children would you

expect to be male and female using

punnett square as you can see in the

picture shown

50

will be male and another 50 percent will

be female

now let us proceed to the three kinds of

sex related inheritance number one sex

linked traits these are inherited

through the x chromosomes only

number two sex influence traits this

occur when phenotypes are different

between males and females with the same

genotype these are expressed in both

sexes but more frequently in one than

the other sex

sex limited traits

these traits can only be expressed in

one sex or the other the traits are not

found on the x and y chromosomes meaning

they are generally autosomal now let us

discuss more about sex-linked traits

let us have an example pattern baldness

pattern baldness

is a recessive sex-linked plate in which

affected people to become bald these are

the genotypes

x dominant b for no baldness and x

recessive b for male pattern baldness

so as you can see these are the

genotypes for female normal

we have female bald

male normal

and male

bald sex link traits are inherited

through the x chromosomes only

males have only one x chromosome thus if

they inherit the affected x

they will have the disorder

females have two x chromosomes therefore

they can inherit or carry the trait

without being affected

if it acts in a recessive manner

let us have an example male with a

disorder mated with a female who is just

a carrier of the disorder

using punnett square let us cross and

show the possible genotype and

phenotypes so as you can see using the

punnett square let us determine the

genotypes and phenotype

these are the possible genotypes

[Music]

how about the phenotypes

25

female normal 25

male normal 25 female bald 25

male bald

so that is how you cross using punnett

square in sex link traits

now for problem number two

this is what you are going to answer in

your notebook or on a piece of paper

screenshot this problem and construct a

punnett square and determine the

possible genotypes and phenotypes

again for mdl students

write your answers on a piece of paper

and for odl students

take a picture of your written answer

and send it or attach it to the

respective assignment in your science

google classroom

so that is all for our lesson for week

four and five i hope you learned

something new today