Lesson 9: Incomplete Dominance
Summary
TLDRThis educational video introduces non-Mendelian inheritance, focusing on incomplete dominance. It explains how traits do not always follow Mendel's laws, leading to phenotypes that are a blend of both parental traits, such as pink flowers from red and white parents. Examples like 4 o'clock flowers and Andalusian chickens illustrate this concept, and the video guides viewers to use Punnett squares to predict genotypic and phenotypic ratios for such inheritance patterns.
Takeaways
- 🌟 The video introduces non-Mendelian inheritance, which includes patterns that do not follow Mendel's laws of inheritance.
- 🔍 It focuses on the concept of incomplete dominance, where the phenotype of the offspring is a blend of the parents' traits.
- 🌺 An example of incomplete dominance is given with flowers, where a cross between red and white flowers results in pink flowers.
- 🐔 The Andalusian chicken is used as another example, where black and white feathered parents produce blue-feathered offspring, illustrating co-dominance.
- 🧬 The video explains that in co-dominance, both alleles are expressed in the phenotype, unlike typical Mendelian dominance.
- 📊 Viewers are expected to use a Punnett square to solve for non-Mendelian inheritance problems by the end of the video.
- 📚 A review of Mendelian inheritance terminologies is prompted, including dominant traits, homozygous, recessive traits, monohybrid cross, heterozygous, and phenotype.
- 🌼 The video script includes a sample problem using a Punnett square to determine the genotypic and phenotypic ratios for flower color crosses.
- 🔢 The genotypic ratio for a cross between a pink and a white flower is 50% heterozygous pink and 50% homozygous recessive white, resulting in a 1:1 ratio.
- 🎨 For a cross between two pink flowers, the genotypic ratio is 25% homozygous dominant red, 50% heterozygous pink, and 25% homozygous recessive white, leading to a 1:2:1 ratio.
- 📈 The phenotypic ratio for the cross between two pink flowers is 25% red, 50% pink, and 25% white, also reflecting a 1:2:1 ratio.
- 👋 The video concludes with an invitation to subscribe for more science educational content.
Q & A
What is non-Mendelian inheritance?
-Non-Mendelian inheritance refers to any pattern of inheritance where traits do not segregate according to Mendel's laws, which describe the inheritance of traits linked to single genes on chromosomes in the nucleus.
What are the types of inheritance patterns that fall under non-Mendelian inheritance?
-Incomplete dominance, sex-linked traits, and multiple alleles are the patterns of inheritance that fall under non-Mendelian inheritance, although the script focuses only on incomplete dominance.
What is incomplete dominance?
-Incomplete dominance is a genetic phenomenon where neither allele is completely dominant over the other, resulting in a phenotype that is a blend of both parental traits.
How does the phenotype of the F1 generation differ in incomplete dominance from Mendelian inheritance?
-In incomplete dominance, the F1 generation exhibits a phenotype that is intermediate between the phenotypes of the homozygous dominant and homozygous recessive parents, rather than expressing only the dominant trait as in Mendelian inheritance.
What is an example of incomplete dominance in flowers?
-An example of incomplete dominance in flowers is seen in 4 o'clock flowers, where a cross between a homozygous red flower and a homozygous white flower results in pink flowers due to the blending of the red and white alleles.
What is the concept of co-dominance mentioned in the script?
-Co-dominance is a genetic phenomenon where both alleles are expressed in the phenotype, neither being completely dominant or recessive. An example given is the Andalusian chicken, where black and white feathers result in blue offspring.
What is the purpose of using a Punnett square in the context of the video?
-A Punnett square is used to predict the genotypes and phenotypes of the offspring in a genetic cross, helping to solve for non-Mendelian inheritance patterns such as incomplete dominance.
What is the genotypic ratio in the cross between a pink and a white flower, according to the script?
-The genotypic ratio in the cross between a pink and a white flower is 50% heterozygous pink and 50% homozygous recessive white, resulting in a 1:1 ratio.
What is the phenotypic ratio when a pink flower is crossed with another pink flower?
-The phenotypic ratio when a pink flower is crossed with another pink flower is 25% red, 50% pink, and 25% white, resulting in a 1:2:1 ratio.
What is the significance of the term 'heterozygous' in genetics?
-Heterozygous refers to an individual that has two different alleles for a particular gene, one inherited from each parent. In the context of incomplete dominance, a heterozygous individual will display a phenotype that is intermediate between the two homozygous parents.
What is the definition of 'homozygous dominant' and 'homozygous recessive' as per the script?
-Homozygous dominant refers to an individual with two dominant alleles for a trait, while homozygous recessive refers to an individual with two recessive alleles. In the script, these terms are used to describe the parental flowers in a genetic cross.
Outlines
🌟 Introduction to Non-Mendelian Inheritance
This paragraph introduces the concept of non-Mendelian inheritance, contrasting it with Mendel's laws of inheritance which describe the inheritance of traits linked to single genes. Non-Mendelian inheritance includes patterns where traits do not segregate according to Mendel's laws. The video focuses on incomplete dominance, a phenomenon where the dominant allele does not completely mask the recessive allele, resulting in a phenotype that is a blend of both. The paragraph sets the stage for the educational content, asking viewers to recall and define key genetic terms such as dominant traits, homozygous, recessive traits, monohybrid cross, heterozygous, and phenotype.
🌸 Exploring Incomplete Dominance
This section delves into the specifics of incomplete dominance, using the example of flower color in plants to illustrate the concept. It explains that when a homozygous dominant and a homozygous recessive flower are crossed, the resulting F1 generation exhibits a phenotype that is intermediate to the two parents, such as pink flowers from a red and white cross. The paragraph further clarifies the concept with additional examples, such as the Andalusian chicken, where the offspring of black and white feathered parents have blue feathers, demonstrating co-dominance where both alleles are expressed. The video script guides viewers to understand how to solve for non-Mendelian inheritance patterns using a Punnett square.
📊 Applying Punnett Square to Incomplete Dominance
The final part of the script provides a practical application of the Punnett square to predict the genotypic and phenotypic ratios in crosses involving incomplete dominance. Two sample problems are presented: one cross between a pink and a white flower, resulting in a 1:1 ratio of heterozygous pink to homozygous recessive white; and another cross between two pink flowers, leading to a 1:2:1 ratio of homozygous dominant red, heterozygous pink, and homozygous recessive white. The paragraph concludes with the expected phenotypic ratios, which mirror the genotypic ratios, reinforcing the understanding of incomplete dominance and its observable outcomes in genetic crosses.
Mindmap
Keywords
💡Non-Mendelian Inheritance
💡Incomplete Dominance
💡Punnett Square
💡Dominant Traits
💡Homozygous
💡Recessive Traits
💡Monohybrid Cross
💡Heterozygous
💡Phenotype
💡Genotype
💡Co-Dominance
Highlights
Introduction to non-Mendelian inheritance, a concept where traits do not follow Mendel's laws.
Mendel's laws describe inheritance of traits linked to single genes in the nucleus.
In non-Mendelian inheritance, traits like incomplete dominance, sex-linked traits, and multiple alleles are observed.
Incomplete dominance is the focus of the video, where the dominant allele does not completely mask the recessive allele.
The video expects viewers to use a Punnett square to solve for non-Mendelian inheritance by the end.
Review of Mendelian inheritance terminologies such as dominant traits, homozygous, recessive traits, etc.
A homozygous dominant and homozygous recessive flower cross results in an unexpected pink flower in the F1 generation.
Explanation of incomplete dominance using the example of 4 o'clock flowers, where red and white blend to produce pink.
Andalusian chicken example where black and white feathers result in blue offspring, illustrating co-dominance.
Blood typing as another example of co-dominance in genetics.
Using a Punnett square to determine the genotypic and phenotypic ratios in non-Mendelian inheritance.
Cross between a pink and white flower resulting in a 1:1 ratio of heterozygous pink to homozygous recessive white.
Cross between two pink flowers resulting in a 1:2:1 ratio of homozygous dominant red to heterozygous pink to homozygous recessive white.
Phenotypic ratio in the cross of two pink flowers is 1:2:1 for red, pink, and white flowers respectively.
Encouragement to subscribe for more science educational videos.
Transcripts
[Music]
hello students
welcome back to our science video i will
introduce to you a new concept in
genetics
which is the counterpart of mendelian
inheritance
this topic is non-mendelian inheritance
it is any pattern of inheritance in
which traits do not segregate
in accordance with mendel's laws these
laws describe
the inheritance of traits linked to
single genes on chromosomes
in the nucleus incomplete dominance
sex-linked traits and multiple alleles
are the pattern of inheritance under
this law
but for today's topic we will only cover
incomplete dominance
at the end of this video viewers are
expected to
use the punnett square to solve for
non-mendelian inheritance
but before we start with our lesson
let's review or recall first
some of the terminologies we discussed
about mendelian inheritance
in the comment section below type your
answer for the definition or meaning of
each word
based on our discussion in mendelian
inheritance
the following words are dominant traits
homozygous dominant recessive traits
monohybrid cross heterozygous
and phenotype
to start this lesson let's analyze the
given picture
based on the picture there is a
homozygous dominant thread
and a homozygous recessive white flower
being crossed in the p
generation in mandela inheritance the
phenotype in the f1 generation should be
read
following the idea of law of dominance
wherein
the presence of one dominant allele will
express a dominant trait
but in this picture the offspring in the
f1 generation is a pink flower
and more pink flowers are produced in
the f2 generation
this concept in genetics reveals the
concept of
incomplete dominance
what is incomplete dominance
one allele doesn't completely mass the
other resulting somewhere in between
it only means that the dominant allele
did not completely mass
or cover the other allele that result in
the combination of both alleles
as an example in 4 o'clock flowers
neither red or white is dominant when a
homozygous red flower
mixed with the homozygous white flower
the alleles blend in the hybrid
to produce pink flowers
[Music]
another example is in andalusian chicken
neither black or white are dominant the
offspring of a black feathered chicken
and a white feathered chicken are blue
this concept in genetics
is co-dominance wherein both dominant
alleles
are expressed another example of
co-dominance
is in the blood typing this topic
will be discussed more
in multiple alleles
let's try to solve sample problems and
determine the pinot peak and genotypic
ratio
using the punnett square
[Music]
show the cross between a pink and a
white flower
the possible pinot types and genotypes
of the cross are the following
pink white pink
and white based on the punnett square
the genotypes are 50 percent
heterozygous pink
and 50 homozygous recessive white that
gives ones to one ratio
while for the pinot types we have fifty
percent pink
and fifty percent white that also gives
one is to one ratio
show the cross between a pink and
another pink flower
the possible pinot types and genotypes
of the cross are the following
red pink another pink
and white based on the punnett square
the genotypes are 25
homozygous dominant red 50 percent
heterozygous pink
and 25 percent homozygous recessive
white that gives one
to two is to one ratio while for the
phenotypes
we have 25 red 50
pink and 25 percent white that also
gives ones to two is to one ratio
thank you for watching do not forget to
subscribe for more science educational
videos
تصفح المزيد من مقاطع الفيديو ذات الصلة
Incomplete Dominance and Codominance (Non- Mendelian Genetics)
NON-MENDELIAN GENETICS: CODOMINANCE || GRADE 9 SCIENCE _ BIOLOGY
Non-Mendelian Inheritance | Grade 9 Science Quarter 1 Week 4-5 | Maestrang Techy
Punnett Squares - Basic Introduction
Codominance and Incomplete Dominance: Non-Mendelian Genetics
S9Q1W4-5 | Non-Mendelian Inheritance
5.0 / 5 (0 votes)