NON-MENDELIAN GENETICS: SEX-LINKED TRAITS | SEX INFLUENCED TRAITS | SEX-LIMITED TRAITS | SCIENCE 9

Summary

This educational video discusses non-Mendelian genetics, focusing on sex-linked traits like color blindness and hemophilia, which are controlled by the X chromosome and affect males more due to their single X. It explains autosomal traits influenced by sex hormones, such as baldness, and sex-limited traits like lactation. The script uses Punnett squares to illustrate inheritance patterns, emphasizing the impact of sex on trait expression.

Takeaways

• 🧬 Non-Mendelian genetics includes phenomena like incomplete dominance, co-dominance, and multiple alleles, where traits may not follow the simple dominant-recessive patterns described by Mendel.
• 🌟 Incomplete dominance results in an intermediate phenotype, while co-dominance expresses both alleles equally in the phenotype.
• 🔬 Multiple alleles occur when there are more than two variants of a gene that control a particular trait.
• 🧬 Humans have 46 chromosomes, with 22 pairs of autosomes and one pair of sex chromosomes determining the sex of the individual.
• 👦 Males have XY sex chromosomes, and females have XX, with autosomal chromosomes being the same for both sexes.
• 🤔 The probability of having a male or female offspring is 50% due to the random assortment of X or Y chromosome from the father.
• 🧬 Sex-linked traits are controlled by genes on the sex chromosomes and can affect both males and females, but males are more susceptible due to having only one X chromosome.
• 👓 Examples of X-linked traits include color blindness and hemophilia, which are recessive and can be more prevalent in males.
• 📊 Punnett Squares are used to predict the genotypes and phenotypes of offspring based on the genotypes of the parents.
• 🦲 Sex-influenced traits like baldness are expressed differently in males and females due to hormonal influences, with males requiring only one recessive allele to express the trait.
• 🍼 Sex-limited traits, such as lactation, are expressed exclusively in one sex, despite being carried by the genes of both sexes.

Q & A

What are the three forms of non-Mendelian genetics mentioned in the script?

The three forms of non-Mendelian genetics mentioned are incomplete dominance, co-dominance, and multiple alleles.

What is the definition of incomplete dominance in genetics?

Incomplete dominance is a form of inheritance where the dominant trait is not completely dominant over the other allele, resulting in an intermediate phenotype.

How does co-dominance differ from incomplete dominance in terms of phenotype expression?

In co-dominance, both alleles are expressed equally in the phenotype, meaning both traits are observed or expressed, unlike incomplete dominance where the phenotype is intermediate.

What is the typical chromosome composition for humans in terms of autosomes and sex chromosomes?

Most humans have 46 chromosomes, consisting of 22 pairs of autosomes and one pair of sex chromosomes. Males have XY sex chromosomes, while females have XX.

How does the sex chromosome composition affect the probability of having male or female offspring?

The composition of sex chromosomes determines the sex of the offspring. A male offspring is produced when an egg is fertilized by a sperm carrying a Y chromosome, while a female offspring results from a fertilized egg by a sperm carrying an X chromosome, leading to a 50% probability for each.

What are sex-linked traits and how do they differ from autosomal traits?

Sex-linked traits are those controlled by genes on the sex chromosomes and can affect both males and females, but may manifest more prominently in one sex. They differ from autosomal traits, which are not influenced by sex chromosomes.

Why are males more susceptible to X-linked traits than females?

Males are more susceptible to X-linked traits because they have only one X chromosome, so if it carries a recessive gene for a disorder, they will express the trait since there is no second X chromosome to potentially mask it.

What is color blindness, and how is it inherited according to the script?

Color blindness is the inability to distinguish certain colors, particularly green. It is an X-linked recessive trait, meaning a person will be colorblind if they inherit the recessive gene from both parents for females or from the mother for males.

How does the Punnett Square help in determining the genotypes and phenotypes of offspring in the context of sex-linked traits?

The Punnett Square is a diagram used to predict the genotypes and phenotypes of offspring by combining the genotypes of the parents. It helps visualize the possible combinations of alleles that the offspring can inherit, especially for traits like color blindness that are sex-linked.

What is the difference between sex-influenced traits and sex-limited traits, as mentioned in the script?

Sex-influenced traits are autosomal traits that are affected by sex hormones and may manifest differently in males and females due to hormonal differences. Sex-limited traits, on the other hand, are traits that are expressed exclusively in one sex, such as lactation being limited to females.

How does the hormonal influence affect the expression of sex-influenced traits like baldness?

The hormonal influence affects the expression of sex-influenced traits by causing a difference in the expression threshold between males and females. For example, baldness is influenced by testosterone levels, which are higher in males, so males with even one recessive allele for baldness may show the trait, whereas females typically need two recessive alleles.

Outlines

00:00

🧬 Introduction to Non-Mendelian Genetics and Sex-Linked Traits

This paragraph introduces the concept of non-Mendelian genetics, focusing on incomplete dominance, co-dominance, and multiple alleles. It explains that incomplete dominance results in an intermediate phenotype, co-dominance expresses both alleles equally, and multiple alleles involve more than two variations of a gene. The paragraph transitions into a discussion about human chromosomes, explaining the composition of autosomes and sex chromosomes, and how they determine the sex of an individual. It also introduces sex-linked traits, which are controlled by genes on the sex chromosomes and can affect both males and females differently, with examples like color blindness and hemophilia. The explanation includes the inheritance patterns of these traits and how they manifest differently in males and females due to the presence of only one X chromosome in males.

05:04

👦👧 Inheritance Patterns of Sex-Linked Traits: Color Blindness and Hemophilia

This paragraph delves into the inheritance patterns of two specific sex-linked traits in humans: color blindness and hemophilia. It provides a detailed explanation of how these traits are inherited, using Punnett squares to illustrate the possible genotypes and phenotypes of offspring from parents with different combinations of these traits. The summary highlights the increased susceptibility of males to sex-linked disorders due to having only one X chromosome, which, if carrying a recessive disease-causing gene, will manifest the disorder. The paragraph also presents hypothetical scenarios involving parents with normal vision and color blindness, as well as carriers of hemophilia and normal males, to demonstrate the probabilities of their offspring inheriting these conditions.

10:07

🦲 Understanding Sex-Influenced and Sex-Limited Traits

The final paragraph shifts the focus to sex-influenced and sex-limited traits. It explains that sex-influenced traits, such as baldness, are autosomal traits that are expressed differently in males and females due to hormonal influences, with males being more likely to express the trait due to higher levels of testosterone. The paragraph outlines the genetic table for baldness and contrasts the expression of the trait in males and females. It also introduces the concept of sex-limited traits, which are traits expressed exclusively in one sex, using lactation as an example. The summary clarifies that while all cattle carry the gene for lactation, the trait is only expressed in females, regardless of the presence of dominant or recessive genes in males. The paragraph concludes with an invitation for viewers to subscribe and stay updated for more educational content.

Keywords

💡Non-Mendelian Genetics

Non-Mendelian genetics refers to patterns of inheritance that do not follow the simple dominant-recessive relationships proposed by Gregor Mendel. In the video, this concept is introduced to explain more complex genetic phenomena such as incomplete dominance, co-dominance, and multiple alleles, which are essential for understanding the diversity of traits in organisms.

💡Incomplete Dominance

Incomplete dominance is a type of genetic inheritance where the dominant allele does not completely mask the effect of the recessive allele, resulting in a phenotype that is intermediate between the two. The video uses this term to illustrate how certain traits, such as flower color in plants, can manifest in a blend of both parental characteristics.

💡Co-Dominance

Co-dominance occurs when two different alleles at the same genetic locus are both expressed in the phenotype. The video explains this concept by stating that in co-dominance, both traits are visible, providing an example of how certain genetic traits can be expressed equally in an organism.

💡Multiple Alleles

Multiple alleles refer to the existence of more than two variants of a gene that are found at a single locus on a chromosome. The video mentions this concept in the context of how a single gene can have different forms, contributing to the genetic diversity seen in populations.

💡Sex Chromosomes

Sex chromosomes are the chromosomes that determine the sex of an organism. In humans, they are denoted as X and Y chromosomes, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY). The video discusses how sex chromosomes play a crucial role in determining the sex of offspring and in the inheritance of sex-linked traits.

💡Autosomal Chromosomes

Autosomal chromosomes are all the chromosomes in an organism's genome that are not sex chromosomes. Humans typically have 22 pairs of autosomes, which are the same in both males and females. The video explains that autosomal chromosomes contain genes that are not linked to the determination of sex and are involved in various other traits.

💡Sex-Linked Traits

Sex-linked traits are genetic traits that are associated with the sex chromosomes. The video describes how these traits can affect both males and females but may be more prevalent in one sex due to the different composition of sex chromosomes. Examples given in the video include color blindness and hemophilia, which are X-linked recessive disorders.

💡X-Linked Traits

X-linked traits are those determined by genes located on the X chromosome. Since males have only one X chromosome, they are more susceptible to X-linked recessive disorders. The video uses color blindness as an example of an X-linked trait, explaining how it is inherited and affects males and females differently.

💡Y-Linked Traits

Y-linked traits are determined by genes on the Y chromosome and are therefore only passed from father to son. The video briefly mentions Y-linked traits, such as hypertrichosis, a condition characterized by excessive hair growth, particularly on the ears, which is exclusive to males.

💡Punnett Square

A Punnett square is a simple diagram used to predict the genotypes of offspring in a genetic cross. The video demonstrates the use of Punnett squares to determine the possible genotypes and phenotypes of offspring for various genetic scenarios, such as when a carrier of a sex-linked trait mates with an unaffected individual.

💡Sex-Influenced Traits

Sex-influenced traits are autosomal traits that are expressed differently in males and females due to hormonal or other sex-related factors. The video uses baldness as an example of a sex-influenced trait, explaining that it is more common in males due to the influence of testosterone.

💡Sex-Limited Traits

Sex-limited traits are those that are expressed in only one sex, even though the genes controlling them may be present in both sexes. The video provides lactation as an example of a sex-limited trait, which occurs only in female mammals despite the presence of the lactation gene in both sexes.

Highlights

Introduction to non-Mendelian genetics, including incomplete dominance and co-dominance.

Incomplete dominance results in an intermediate phenotype between dominant and recessive traits.

Co-dominance is characterized by the equal expression of both alleles in the phenotype.

Multiple alleles allow for more than two variations of a trait controlled by a single gene.

Explanation of human chromosome composition, including autosomes and sex chromosomes.

Sex chromosomes determine the sex of an organism, with XY for males and XX for females.

Sex-linked traits are recessive and can affect both males and females differently.

Examples of X-linked traits include color blindness and hemophilia.

Y-linked traits, such as hypertrichosis, are exclusive to males.

Genetic table and Punnett square demonstration for predicting offspring traits in color blindness.

Males are more susceptible to X-linked traits due to having only one X chromosome.

Hemophilia is a serious X-linked trait that affects blood clotting.

Genetic table for hemophilia, showing carrier and affected individuals among males and females.

Sample problem solving using Punnett square for predicting hemophilia in offspring.

Introduction to sex-influenced traits, which are autosomal traits affected by sex hormones.

Baldness as an example of a sex-influenced trait, with different genetic requirements for expression in males and females.

Genetic table for baldness, illustrating the difference in expression between males and females.

Sample problem solving for predicting baldness in offspring of heterozygous not bald females and homozygous bald males.

Sex-limited traits are those expressed only in one sex, such as lactation in females.

Final summary and invitation to subscribe for more educational content.

Transcripts

[Music]

good day Learners Welcome to our new

lesson in our previous discussion we

talk about some of the non-mendelian

genetics such as incomplete dominance

co-dominance and multiple alleles

incomplete dominance is a form of

inheritance in which the dominant trait

is not completely dominant over the

other allele and the resulting phenotype

is intermediate meanwhile in

co-dominance both alleles are expressed

equally in the phenotype of the head

they recycle which means both traits are

observed or expressed in the phenotype

on the other hand multiple alleles are

the traits controlled by a single Gene

with more than two alleles for today's

lesson we are going to talk about

another non-mendelian genetics most

humans have 46 chromosomes 22 pairs of

autosomes or somatic chromosomes and one

pair of sex chromosomes sex chromosomes

control whether the organism will be

male or female

males have 44 autosomes plus XY sex

chromosomes while female have 44

autosomes plus XX sex chromosomes

both males and females have 22 pairs of

autosomal chromosomes an affair of sex

chromosomes a male offspring will be

produced when an egg is fertilized by a

sperm carrying a Y chromosomes similarly

a female Offspring will be result of a

fertilized egg to a sperm carrying an X

chromosome therefore there is a 50

probability of having male and female

Offspring not all traits are controlled

by alleles found in autosomes there are

traits governed by the sex chromosomes

and these traits are called The Sex

sling traits sex-linked traits are

recessive traits these are the traits

that are found on either one of the sex

chromosomes sex-link traits affect both

males and females but in some cases one

particular sex is more prone to have a

sex literary a sex-linked trait is a

trait genetically determined by an

allele located on the sex chromosome a

rate that is determined by the allele on

the X chromosomes is particularly

described as the x-linked traits whereas

the traits that determined by the allele

on the Y chromosomes is said to be the

y-elect traits an example of excellent

traits is color blindness and hemophilia

on the other hand an example of wyling

traits is hypertrichosis which is

characterized by hairy ears these traits

is exclusive only to meals now let's

talk about the genetic table of

colorblind color blindness is the

inability of a person to distinguish

colors especially green a person will be

colorblind if he or she inherit

recessive genes from parrots now let's

take a look at the genotypes and

phenotypes of female

this one is for the normal female

and this one for the carrier female that

means she has a normal vision because

Sex Link traits are recessive genes and

it can be masked by the other healthy X

chromosomes therefore since she is a

carrier she will have the hidden traits

of being colorblind which can be passed

to her Offspring and this one is for

color blind female a female can have

colorblind Vision if both X chromosomes

carry the colorblind traits now let's

take a look at the genotypes and

phenotypes of male this one is for the

normal meal and this one is for the

color blind me

now as you can see males are easily

affected by the x-link trees because

they only have one copy of X chromosomes

and ones that one copy of X chromosomes

carries x-link trace the male will have

sex linked disorder let's have an

example

Aina having a normal vision married a

man who is a color blind what will be

the genotype and phenotype of their

offspring and how many percent of their

offspring will have a colorblind Vision

now we're going to solve it using the

Punnett Square remember our first step

is to determine the genotypes of the

parents and based on the problem the

parents are normal females and color

blind males now this is the genotype of

a normal female

and this one is for the color blind me

now let us solve it using the Punnett

Square

once done we're going to summarize the

results write down the genotype and the

phenotypes of The Offspring now this is

our genotype we have to carrier female

and two normal male and the genotypic

ratio is 2 is the two for the phenotype

we have 50 carrier female and 50 normal

meal now another example of excellent

traits in human is hemophilia a person

suffering from hemophilia could die from

loss of blood even from a small wound

because the blood either clots very slow

or does not clot at all now let's take a

look at the genotypic table or the

genetic table of Hemophilia this one is

for the normal female

this is the carrier female it means she

has the hidden traits of Hemophilia

which can be passed to her offspring

this is for hemophilic females since

both eggs carry hemophilic trees now

let's take a look at the genotypes and

phenotypes of a male

this is for normal meal and this one is

for hemophilic meal now as I mentioned a

while ago males are prone to sex sling

traits because males have only one X

chromosomes and once it is affected they

will have the disorder now let's have

sample problem 2. hemophilic carrier

female married a normal meal what will

be the genotypes and phenotypes of their

offspring and how many percent of their

offspring will have hemophilia

the first step is to determine the

genotypes of the parents and based on

the problem the parents are hemophilic

carrier female and a normal male now

this is the genotype for hemophilic

Carrier female and a normal male now

we're going to solve it using Punnett

Square

once done we're going to summarize the

result write down the genotypes and

phenotypes of new obstring now this is

the genotype of The Offspring we have

one normal female one carrier female one

normal male and one hemophilic meal and

this is the genotypic ratio we have one

S21 is to one is to one and the

phenotype is 25 normal female 25 carrier

female 25 normal male and 25

hemophilic meal

now let's talk about sex influence trees

sex influence traits or autosomal traits

that are influenced by the sex

chromosomes it is also a recessive

traits one of the example of sex

influence trait is baldness and is

influenced by the hormone testosterone

and since males have a higher level of

testosterone compared to females if a

male has one recessive allele he will

show that trait but it will take more

assessment for the female to show the

Savory now let's take a look at the

genetic table of baldness here we're

going to represent baldness as a small

letter B since it is a recessive traits

now this is for the genotypes and

phenotypes of female

as you can see for the female to become

bald it needs two recessive genes of

bulb now let us compare it to male

as you can see males only need one

recessive gene of baldness to become

bald that is because baldness is

influenced by the hormone testosterone

which is men produce higher amounts

compared to women now let's have sample

problem number three a heterozygous not

bad female married a homozygous bald man

what will be the genotypes and

phenotypes of their offspring and how

many percent of their offspring will be

bald first we're going to determine the

genotypes of the parents and based on

the problem the parents are heterozygous

not bald and a homozygous bald man the

genotype of the heterozygous not bald

female is this one why because when we

say hetero that means different this

genotype has two different genes just

look at the symbol the other one has a

capital letter B while the other one has

a small letter B the small letter B

carries the gene for baldness this

genotype is considered not bugged

because baldness is recessive gene which

means it is a hidden tree now the

genotype for homozygous mold is this one

why because hormone means the same and

this genotype carries the same genes in

which the same small letter b and small

B indicates baldness now let us solve it

using Punnett Square

once done we're going to summarize the

result by writing the zero type and

phenotypes of The Offspring

now let's talk about sex limited traits

sex-limited traits are those traits

limited to only one sex lactation is a

good example of sex limited trait that

is exclusively among females however

cattle carries Gene for lactation in

both males and females

lactating Gene is a dominant gene over

non-lactating recessive gene and female

cattle carrying one dominant gene or two

dominant genes lactation will be shown

nevertheless neither male cattle having

the dominant genes nor male cattle that

have recessive genes will update so

that's it see you in our next lesson and

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