Transcript File - Ms. D. Science CGPA

Human Genetics and Genetic TechnologyCourse 2
13-1 Human Inheritance
Ms. De Los Rios
7th Grade
Vocabulary
1. Sex chromosomes – A pair of chromosomes carrying genes
that determine whether a person is male or female.
2. Sex-linked gene- A gene that is carried on a sex (X or Y)
chromosome.
3. Carrier- A person who has one recessive allele and one
dominant allele for a trait.
My Planet Diary pg. 444
Posted by: Julian
Location: Rockledge, Florida
I have noticed that there are a lot of physical traits that run in my
family. It seems like poor eyesight is common. Both sets of my
grandparents have poor eyesight and wear glasses. Both of my
parents have poor vision and here I am, yes, I too have to wear
glasses. Genetics rules.
What characteristics do you have that resemble those of your
relatives? ____________________________________________
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What Are Some Patterns Of Human
Inheritance? Pg. 444
Look at the students in your classroom. Some have curly
hair and others have straight hair. Some people are tall, some are
short and others are in between.
The different traits you see are determined by a variety of
inheritance patterns.
Some human traits are controlled by single genes with two alleles,
and others by single genes that have multiple alleles. Still other
traits are controlled by many genes that act together.
Single Genes With Two Alleles
Human traits that are controlled by a single gene with either a
dominant or a recessive allele, such as a dimpled chin, or
widow’s peak produce two distinctly different physical
appearances, or phenotypes.
Single Genes With Multiple Alleles
Some traits are controlled by a single gene that has more than two
alleles (multiple alleles- 3 or more forms of a gene that code for a
single trait).
Human blood type is controlled by a gene with multiple alleles.
There are 4 main blood types- A, B, AB, and O.
Three alleles control the inheritance of blood types.
AB blood type is codominant which means that both alleles for the
gene are expressed equally. If you get an A allele from one parent
and a B allele from the other you can have type AB blood.
Apply It! Human Inheritance pg. 445
Inheritance of Blood Type
The table shows which combinations of alleles result in each human blood type.
1. Interpret Tables- Genotypes are listed in the (left/right) column of the table, while
phenotypes are on the (left/right).
2. Infer- Why are there more genotypes than phenotypes for blood types?
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Traits Controlled by Many Genes
Some human traits show a large number of phenotypes because the
traits are controlled by many genes. The alleles of the different
genes act together as a group to produce a single trait.
At least 4 genes control height in humans.
You can see the extreme range of heights
in the picture.
Skin color is another human trait
that is controlled by many genes.
Some Genetic Traits
.
Assess Your Understanding pg. 446
1a. Explain- Why do some traits exhibit a large number of
phenotypes? _________________________________________
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b. Draw Conclusions- Aaron has blood type O. Can either of his
parents have blood type AB? Explain your answer.
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I get it! Now I know that some human traits are controlled by_______
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What are the Functions of the Sex
Chromosome? Pg. 446
The body cells of humans contain 23 chromosome pairs, or 46
chromosomes. The sex chromosomes are one of these pairs.
The sex chromosomes carry genes that determine a person’s
gender as being either male or female. They also carry genes
that determine other traits.
Girl or Boy?
The sex chromosomes are the only
chromosome pair that doesn’t always match.
Girls have 2 X chromosomes XX
Boys have an X and a Y
XY
The Y chromosome is much smaller
than the X chromosome.
Sex Chromosome and Fertilization pg. 447
While all eggs carry one X chromosome, sperm cells carry either an
X or a Y chromosome. When an egg is fertilized by a sperm cell,
the sex chromosome carried by the sperm cell determines
whether a child will be a girl (X) or a boy (Y).
So…. The father determines the sex of the baby!!!!!!
Figure 3- Complete the Punnett
square to show the possible
genotypes and phenotypes of a
child.
Determine- What is the probability
that the child will be a girl? A boy?
Interpret Diagrams- What sex will
the child be if a sperm with a Y
chromosome fertilizes an egg.
Sex- Linked Genes pg. 448
Genes found on the X and Y chromosomes are often called sex-linked
genes because their alleles are passed from parent to child on a sex
chromosome. Traits controlled by sex-linked genes, such as
colorblindness, are called sex-linked traits.
X and Y Chromosomes
The human X chromosome is larger and carries more
genes than the human Y chromosome.
Sex-linked genes, like other genes, can have dominant and recessive alleles. In
females, a dominant allele on an X chromosome will mask a recessive allele
on the other X chromosome. But in males, because the Y chromosome is
much smaller than the X chromosome, there is usually no matching allele on
the Y chromosome to mask the allele on the X chromosome. So any allele
on the X chromosome, even a recessive allele, will produce the trait in the
male who inherits it.
Inheritance of Colorblindness pg. 449
Colorblindness is a trait controlled by a recessive allele on the X
chromosome. Many more males than females have red-green
colorblindness.
A carrier is a person who has one recessive allele for a trait and one
dominant allele. A carrier of a trait controlled by a recessive allele
does not express the trait, but can pass the recessive allele on to
his or her offspring.
 In the case of sex-linked traits, only females can be carriers
because they are the only ones who can carry two alleles for the
trait.
Figure 6- Colorblindness Punnett Square pg. 449
Red-green colorblindness is a sex-linked trait.
1. Identify- Complete the Punnett square by filling in the child’s genotype, sex,
and phenotype. For each child, draw the correct shape, and color it in to
match the key.
2. Calculate- What is the probability that this Couple will have a colorblind child?
3. Apply Concepts- What allele combination would a daughter need to inherit to
be colorblind?
Assess Your Understanding pg. 449
2a. Review- What is the sex of a person who is a carrier for
colorblindness? ___________________________________
b. Challenge- Mary and her mother are both colorblind. Is Mary’s
father colorblind, too? How do you know?________________
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I get it! Now I know that the functions of the sex chromosomes
are ______________________________________________
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