3.7 Genetics, populations, evolution and ecosystems

Question 1

What is the genotype?

Answer 1

The genetic constitution of an organism

Question 2

What is the phenotype?

Answer 2

The expression of the genetic constitution and its interaction with the environment

Question 3

In a diploid organism, the alleles at a specific locus may be either…

Answer 3

Homozygous or heterozygous

Question 4

Define Homozygous alles

Answer 4

Both alleles at a specific locus on each homologus chromosomes are the same

Question 5

Define Heterozygous alleles

Answer 5

Both alleles at a specific locus on each homologous chromosome are different

Question 6

Alleles can be what?

Answer 6

Dominant
Recessive
Codominat

Question 7

Define a dominant allele

Answer 7

The allele that is expressed in the phenotype in a heterozygous state

Question 8

Define a Recessive allele

Answer 8

The allele that isnt expressed in the phenotype in a heterozygous state. Only expressed if homozygous recessive

Question 9

Define a codominate allele

Answer 9

Both alleles for same gene in heterozygous organism contribute to phenotype

Question 10

What is used to represent a dominant allele

Answer 10

Capital Letter

Question 11

What is used to represent a recessive allele

Answer 11

Lowercase letter

Question 12

What are monohybrid crosses used for?

Answer 12

Inheritance of one characteristic controlled by a single gene

Question 13

What is the common ratio for monohybrid crosses?

Answer 13

3:1

Question 14

What are dihyrbid crosses used for?

Answer 14

The inheritance of two different characteristics controlled by two different characteristics

Question 15

What is the common ratio for dihyrbid crosses?

Answer 15

9:3:3:1

Question 16

When do you use codominace crosses?

Answer 16

Both alleles in heterozygous individuals contribute to the phenotype

Question 17

What is the common ratio for comindance ratio?

Answer 17

1:2:1

Question 18

When are crosses involving multiple alleles used?

Answer 18

When a gene may have more than two alleles

Question 19

What is an example of multiple allele crossing?

Answer 19

Inheritance of human blood groups

Question 20

When is a gene “sex-linked”?

Answer 20

If its locus is on the sex-chromosomes, X and Y

Question 21

What properties are ideal for a organism used to study genetic crosses?

Answer 21

A large number of eggs
Small size so reduced costs to store
Easy to identify
Short generation times → reproduce quicker so faster results

Question 22

Why may the observed ratios calculated not be the same as the expected ratios in inheritance?

Answer 22

Fertilisation is random

Selection advantage or disadvantage

Question 23

Why are males more likely to express a recessive allele carried on the X-chromosome than females?

Answer 23

Only 1 copy of the gene/allele

Cant be heterozygous

Question 24

Are males or females more likely to carry genetic disorders?

Answer 24

Males - only have two options:
Healthy - X^HY
Disease - X^h Y

( H - healthy, h - Disease )

Question 25

When do we use autosomal linkage?

Answer 25

When two genes are carried on the same autosome ( non-sex linked chromosome)

Question 26

Explain ‘Autosomal Linkage’

Answer 26

Genes on same chromosome so stay together during independent segregation of chromosomes in M1

Linked genes pass into gamete and inherited together

Reduction of possible genotypes in offspring (more offspring with parents genotypes and phenotypes)

Closer together on autosome = more closely linked → crossing over less likely to split

Question 27

When do we use crosses involving epistasis?

Answer 27

The interaction of non-linked genes where one masks the expression of the other