NON-MENDELIAN GENETICS: SEX-LINKED TRAITS | SEX INFLUENCED TRAITS | SEX-LIMITED TRAITS | SCIENCE 9
Summary
TLDRThis 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
🧬 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.
👦👧 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.
🦲 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.
Mindmap
Keywords
💡Non-Mendelian Genetics
💡Incomplete Dominance
💡Co-Dominance
💡Multiple Alleles
💡Sex Chromosomes
💡Autosomal Chromosomes
💡Sex-Linked Traits
💡X-Linked Traits
💡Y-Linked Traits
💡Punnett Square
💡Sex-Influenced Traits
💡Sex-Limited Traits
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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