Medelian Inheritance (notes) 4A

Question 1

Blending theory of inheritance (2)

Answer 1

Hereditary traits blend evenly in offspring through mixing off the parent’s blood.
Offsprings had traits intermediate to parents (traits appearing halfway btwn parents)

Question 2

What type of flower Mendel used and what did he do to them?

Not true breeding one

Answer 2

Mendel used the garden pea because it can be grown easily. Because the flower had both male and female reproductive system, Mendel had to cut off the anthers (male organoid) to cross pollinate

Question 3

Mendel wanted to disapprove —— as he did not —–

Answer 3

blending inheritance as he did not see blending traits with his works with mice/bees

Question 4

In blending inheritance, variation will be

Answer 4

reduced over time (particulary rare traits).
*Dilution
All traits will quickly converge on a blended average, destroying the variation that is necessary for evolution

Question 5

When Mendel started his test, he always used

Answer 5

true breeding

Question 6

What did mendel obeserve and what was his conclusions after crosing the parental generation?

Answer 6

He crossed the homozygous peas and generated the first fillia.The phenotype of the first fillia were all the same and that was the dominant phenotype

Question 7

after generating first fillial what did his results reject?

Answer 7

Rejected blending inheritance as he didnt get a blending colour between yellow or green.

Question 8

How is the phenotype for a dominant allele expressed?

+use peas as example

Answer 8

Often the dominant allele codes for a functional protein wherease the recessive allele does not. Producing protein gives us the phenotype that we want. For ex: pea colour is determined by enyzyme that breaks down chlorophyll so in yellow pea, the allele for yellow codes for an enzyme that breaks down chlorophyll.

Question 9

Dominant allele is always the allele associated with the trait we see in

Type of organism*

Answer 9

heterozygote

Question 10

Monohybrid cross

Answer 10

Using true breeding (offspring with same phenotype) and crossing it with another true breeding with a different phenotype

Question 11

F2 ratio

Answer 11

3:1
Dominant: recessive

Question 12

Principle of segregation is tested by

Answer 12

predicting the outcome of crosses

Question 13

Seeds in F2 showing recessive trait should be

*Not percentage

Answer 13

homozygous recessive (a/a)

Question 14

What was Mendel’s 3 hypotheses?

Answer 14

1. Adults plants carry two copies of factors (genes) that govern theinheritance of a character (e.g. wrinkled versus smooth peas). Based on the combination, you have round peas or wrinkled
2. If an individual’s pair of genes consist of different alleles, one allele is dominant over the other and masks it
3. The pair of alleles that control a character separate as gamestes (meiosis); half of the gamestes carry one allele and the other half carry the other allele. Each gamete receives just one gene copy, which is selected randomly. Diploid organisms get one allele form each parent.

Question 15

probability of a gamete inheriting one of the two alleles during meiosis is —– bc of——-

Answer 15

random because of random alignment of chromosomes at the metaphase plate

Question 16

Probability of a genotype in a cross is determined by

Answer 16

the product of the probabilities of acquiring each gamete from the mother and father

Question 17

homozygous in relationship to principle of segregation

Answer 17

the two alleles are the same therefore produce only one type of gamete

Question 18

Heterozygous in relationship to principle of segregation

Answer 18

The two alleles are different therefore, produces two types of gametes

Question 19

How do you know if you have a heterozygote?

Answer 19

Perform a test cross with homozygous recessive

Question 20

If you have a heterozygous and you test cross it, what is produced?

Answer 20

You will see a 1:1 ratio of dominant and recessive phenotype

Question 21

If you have a homozygous dominant and you test cross it, what is produced?

Answer 21

You will see all dominant phenotype

Question 22

What did Sutton notice? (3)

Answer 22

1. Chromosomes occur in pairs (homologous chromosomes) in diploid organisms
2. Chromosomes of each pair seperated in gametes
3. Seperation of each pair of chromsomes is independent of other pairs

Question 23

Incomplete Dominance (2)

+how this happens

Answer 23

• One allele is not completely dominant to the other allele
  (ex: red+white=pink)
• intermediate phenotype
• Happens when heterozygote plants produce some functional enzyme but not full amount

Question 24

Co-dominance (3)

+what we we dont get?

Answer 24

• Both homozygous phenotypes expressed as dominant alleles fight for expression
• Alleles have equal effect
• We dont get an intermediate phenotype but instead 2 different phenotype expressed in the individual

Question 25

Why is incomplete dominance different than blending inheritance?

Answer 25

Because when we generate our F2, we see the red flowers come back and so we havent lost those traits. They are still behaving as individual discrete.

Question 26

polymorphic

Answer 26

more than 2 alleles

Question 27

Complex traits are—– (3)

+what this mean+ex

Answer 27

• polygenic
• There are multiple genes that are responsible for contributing to that particular phenotype
• Ex: height and other similar features are controlled not by one gene but by multiple genes that make small contributions to the overall outcome (more dominant= longer)

Question 28

What influences create continous distribution?

Answer 28

Genectic and environmental influences

Question 29

For continous distributions, as we increase the ——we get ——–. Within each bar….

Answer 29

• number of genes
• Even finer variations
• There is variation as the environments are different

Question 30

MHC (4)

Tell me about this+ codominant expression

Answer 30

• Group of genes that code for proteins found on the surface of cells that help immune recognize foreign substance.
• Group of genes with each having an unsually large number of alleles
• Very rare for two individuals to have the same set of MHC molecules
• Two alleles of each MHC gene are expressed codominantly in each individual- with the protein products of both the alleles at a locus being expressed in the cell