Genetics, Populations, Evolution And Ecosystems - Inherited Change

Question 1

What does genotype mean?

Answer 1

The alleles an organism has inherited

Question 2

Phenotype definition

Answer 2

An organisms characteristics and its interaction with the environment

Question 3

Dominant definition

Answer 3

An allele that will always be expressed in the phenotype

Question 4

Recessive meaning

Answer 4

An allele only expressed if no dominant allele is present

Question 5

What does codominant alleles mean?

Answer 5

When both alleles are equally dominant and expressed in the phenotype

Question 6

What does multiple alleles mean?

Answer 6

When there are more than two alleles for a single gene

Question 7

What does sex linkage mean?

Answer 7

When a gene locus is on the X chromosome

Question 8

Give the blood groups and their potential genotypes

Answer 8

A: I^A I^O or I^A I^A
B: I^B I^O or I^B I^B
AB: I^A I^B
O: I^O I^O

Question 9

What does the genotype of blood group AB show?

Answer 9

Co-dominance

Question 10

What do blood groups A and B show?

Answer 10

Multiple alleles

Question 11

How is sex genetically determined?

Answer 11

determined by the combination of gametes:
XX is female
XY is male

Question 12

Why do the results from genetic crosses often differ from the predicted results?

Answer 12

Because chance determines which gametes fuse with each other and so it is important to use a large number of organisms in genetic crosses to obtain representative results.

Question 13

What stats test is used in inheritance and what is it used for?

Answer 13

Chi-squared, used to determine if there’s a significant difference between the predicted offspring frequency (ratio) and the actual observed offspring frequency

Question 14

When doing chi-squared what do you say if the calculated value of chi squared is less than the critical value?

Answer 14

Having stated the null hypothesis that there is no significant difference between the expected and observed frequency of x

• There is more than 5% probability that the results are due to chance
• Do not reject null hypothesis / accept null hypothesis so there is no significant difference between the observed and expected results

Question 15

What does epistasis mean?

Answer 15

When one gene influences / masks the expression of another gene

Question 16

Give an example of a sex linked genetic disorder, what its caused by and what it leads to/

Answer 16

Hemophilia specifically X linked, caused by a recessive allele with an altered sequence of DNA nucleotide bases that codes for a faulty protein so the individual cannot produce a functional protein required in the clotting process.

Question 17

Give an example where epistasis occurs and what each of the genes do as well as their alleles

Answer 17

In Mice where several genes determine the coat colour:
- Gene A controls if the hairs are banded
A= hairs with black bands
a = fully black hairs
-Gene B controls coat color
B = hairs are coloured
b = hairs are white so not coloured

Question 18

how does codominance affect the inheritance of characteristics?

Answer 18

As both alleles are equally dominant so both are expressed in the phenotype

Question 19

What is a dihybrid cross?

Answer 19

a genetic cross where where the inheritance of two genes is considered at the same time

Question 20

Using the dihybrid inheritance example of the peas, give the genes, alleles and their corresponding phenotypes.

Answer 20

-Gene 1 codes of shape
R is dominant for round and r is recessive for wrinkled
-Gene 2 codes for the colour
Y is dominant for yellow and y is recessive for green

Question 21

What does crossing over in meiosis mean for inheritance?

Answer 21

Results in the new combination of alleles in the gametes and therefor means predicted gametes in the punnet square may differ.

Question 22

What is autosomal linkage?

Answer 22

When two genes are located on the same chromosome and not on the X and Y chromosome

Question 23

How does autosomal linkage affect the combination of alleles in gametes?

Answer 23

You can only have both alleles as dominant or both alleles as recessive e.g.
AB and ab

instead of AB Ab aB and ab