Genetics And Inheritance

Question 1

What is variation?

Answer 1

Differences between individuals

Often caused by mutations

Question 2

What is the phenotype?

Answer 2

The visible characteristics of an organism

Question 3

Define genotype

Answer 3

The genes that an organism has

Genetic make up

Question 4

Define karyotype

Answer 4

The number and visual appearance of the chromosomes in a cell

Question 5

Give examples of types of mutagens

Answer 5

Physical: X-rays gamma rays uv light

Chemical: reactive oxygen species or mustard gas

Biological: some viruses food contaminants. Jumping genes

Question 6

What are the different types of chromosome mutations?

Answer 6

Deletion
Inversion
Translocation
Duplication
Non disjunction

Question 7

What is a diploid cell?

Answer 7

A cell or organism consisting of two sets of chromosomes

Question 8

Define a haploid cell

Answer 8

Half the diploid number of a somatic cell

Question 9

How does genetic variation arise from sexual reproduction?

Answer 9

In meiosis:

Allele shuffling (crossing over) in prophase 1

Independent assortment of chromosomes in metaphase 1

Independent assortment of chromatids in metaphase/anaphase 2

Also from random fertilisation

Question 10

What environmental factors affect genetic variation

Answer 10

Accents
Body modification
Injuries

Question 11

Define an allele

Answer 11

A version of a gene. (R & r) one gene but two alleles

Question 12

Define dominant allele

Answer 12

Only one copy required to express the phenotype whether it is paired with a hetero or homozygous allele

Question 13

Define recessive allele?

Answer 13

Two homozygous alleles required in order for the phenotype to be expressed

Question 14

Define heterozygous alleles

Answer 14

Different alleles at a particular gene locus

Question 15

Define homozygous alleles

Answer 15

Identical alleles at a particular gene locus

Question 16

Who was Gregor Mendel?

Answer 16

Carried out the pea plant experiment to deduce the monogenic inheritance ratio

(Used pea plants as they are easy to grow and can be cross fertilised)

Question 17

What is mono hybrid inheritance?

Answer 17

Where one characteristic is inherited

Question 18

How can you deduce the genotype from the phenotype?

Answer 18

Carry out a cross with a known strain and look at the phenotypic ratio of the offspring

Question 19

What is dihybrid inheritance?

Answer 19

The simultaneous inheritance of 2 different characteristics

Question 20

What is the expected phenotypic ration with a monohybrid cross?

Answer 20

3:1

Question 21

What is the expected phenotypic ratio with a dihybrid cross?

Answer 21

9:3:3:1

Question 22

What assumptions are made when carrying out a dihybrid cross?

Answer 22

The 2 traits are inherited independently

The two traits are on separate chromosomes

Question 23

What is sex linkage?

Answer 23

Any gene that is carried on the X or Y chromosome is said to be sex linked

Question 24

Why are there potential problems with sex linked inherited genes?

Answer 24

The X chromosome is a lot longer than the Y-chromosome and therefore there is often not the dominant allele on the Y chromosome to pair up with the X chromosome

Question 25

What is haemophilia?

Answer 25

Condition where the blood cannot clot fast enough due to a deficiency in the X chromosome

(Therefore haemophilia is a sex linked genetic disorder)

Question 26

What is codominance?

Answer 26

Where both alleles present in the genotype of a heterozygous individual are express in the phenotype

Question 27

Give an example of codominant genes.

Answer 27

Blood group

I^a I^b are codominant and both dominant over I^o

Question 28

What is autosomal linkage?

Answer 28

Where two genes present on the Same chromosome (not sex chromosome) are inherited together.

Question 29

How may autosomal linkage occur?

Answer 29

Due to crossing over (chiasmata)

Question 30

Why can’t we predict the phenotype of offspring with autosomal linkage using a punnet square and what do we use instead?

Answer 30

Since we cannot predict the number of gametes (recombinant gametes)

Instead we use the chi squared test

Question 31

What do we use the chi squared test for?

Answer 31

Used to determine if the difference between the observed and expected results are significantly

Question 32

What is epistasis?

Answer 32

The interaction on non linked genes where one gene masks the effect of another

Question 33

Define recessive epistasis

Answer 33

When the recessive allele masks the effect of either allele on the second gene

Question 34

Define dominant epistasis

Answer 34

When the dominant allele is one gene masks the effect of either allele on the second gene

Question 35

What is the Hardy Weinburg equation?

Answer 35

P^2 + 2pq + q^2 = 1

P = frequency of dominant allele

Q = frequency of recessive allele

Question 36

What is the Hardy Weinburg principle?

Answer 36

The proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next if the conditions are met.

P + q = 1

Question 37

What are the Hardy Weinburg conditions/ assumptions?

Answer 37

No mutations arise

The population is isolated

No selection occurs

Large population

Random mating

Question 38

How do you work out degrees of freedom?

Answer 38

Number of classes - 1

Question 39

What do a small or large chi squared mean?

Answer 39

Small chi squared = fits the expected ratio

Large chi squared = does not fit the expected ratio

Question 40

What happens if chi squared is greater than the critical value?

Answer 40

The difference between the observed and expected ratios is statistically significant and therefore we can reject the null hypothesis

Question 41

What happens if chi squared is less than the critical value?

Answer 41

The difference between the observed and expected ratio is not statistically significant and therefore we accept the null hypothesis