7A Genetics

Question 1

Gene

Answer 1

A sequence of DNA bases that code for a specific protein which results in a characteristic

Question 2

Allele

Answer 2

Different versions of a gene

Question 3

Diploid organisms

Answer 3

Contain two copies of the same gene (one from each parent) So we have two alleles of each gene

Question 4

Locus

Answer 4

The allele position of a gene on a chromosome pair

Question 5

Genotype

Answer 5

The genetic construction e.g RR or Rr

Question 6

Phenotype

Answer 6

The expression of the genetic constitution and its interaction with the environment- the characteristic that is expressed

Question 7

Codominant

Answer 7

Alleles are expressed equally in the phenotype because neither allele is recessive

Question 8

Homozygous

Answer 8

Two alleles of the same type

Question 9

Heterozygous

Answer 9

Two different alleles

Question 10

Haploid

Answer 10

Gametes contain only one set of chromosomes

Question 11

Dihybrid inheritance

Answer 11

The inheritance of two characteristics which are controlled by different genes

Question 12

Sex-linked

Answer 12

The alleles that code for certain characteristics are located on a sex chromosome

Question 13

Why are sex-linked genotypes usually singular in males?

Answer 13

The gene is only carried on the X chromosome, so in a male, there is only one allele

Question 14

Examples of sex-linked genetic disorders

Answer 14

Colour blindness and haemophilia

Question 15

Autosome

Answer 15

Any chromosome that isn’t a sex chromosome

Question 16

Autosomal genes

Answer 16

Genes located on the same autosome. Genes on the same autosome are said to be linked

Question 17

Linkage of autosomal genes

Answer 17

Stay together during independent segregation of chromosomes in meiosis I and their alleles will be passed on to the offspring together, unless crossing over splits them. Closer two genes are on the autosome, the less likely they are to be separated by crossing over, so the are said to be more closely linked

Question 18

Epistasis

Answer 18

When an allele of one gene blocks the expression of another allele of another gene

Question 19

What is an example of epistasis?

Answer 19

If someone has an allele that codes for baldness, it will block the allele for a widows peak, so the widows peak will not be expressed as a phenotype

Question 20

What is a null hypothesis?

Answer 20

There is no significant difference between the observed and expected results

Question 21

When would you use chi squared?

Answer 21

When dealing with frequencies

Question 22

What does the critical value show?

Answer 22

Gives the level of probability that the difference observed is due to chance

Question 23

When do you reject the null hypothesis?

Answer 23

When the chi squared is less than the critical value