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Flashcards in GENETICS Deck (35)
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1
Q

How does genetic variation occur

A

Inherited mutations during S phase
Crossing over
Independant segregation
Random fertilisation

2
Q

Define epistasis

A

Where an allele of one gene MASKS the expression of another gene
Eg - flower colour

3
Q

Define a gene

A

a sequence of bases on a DNA molecule that codes for a protein which results in a characteristic
eg a gene for eye colour

4
Q

define an allele

A

A different version of a gene
for example the gene is eye colour
the allele could be blue, green or brown

5
Q

What is a genotype

A

the genetic makeup of an organism

what alleles does the organism have?? Aa AA aa

6
Q

what is a phenotype

A

the expression of the genetic makeup and its interaction with the environment
eg brown eyes is shown

7
Q

what is dominant

A

Shown by a capital letter, if one present its shown in phenotype
They over power the other allele
eg AA or Aa

8
Q

what is recessive

A

only shown in phenotype if 2 recessive present
gets overpowered by a dominant allele
eg aa

9
Q

what is codominant

A

Both alleles are expressed in the phenotype, neither one is recessive
eg sickle cell anaemia

10
Q

What is a locus

A

the point on a chromosome where the alleles and genes are found

11
Q

what is homozygous

A

2 copies of the same allele

eg AA or aa

12
Q

what is heterozygous

A

carries 2 different alleles

eg Aa

13
Q

what is a carrier

A

a person which carries an allele which can be passed onto offspring but is not shown in the phenotype
eg haemophilia

14
Q

why are humans diploid

A

contain 2 sets of chromosomes

2 alleles for each gene

15
Q

for a monohybrid cross how many things are crossed

A

2 with 2

eg AA with Aa

16
Q

for a dihybrid cross how many things are crossed

A

4 with 4

eg AaBb with AABB

17
Q

What are the 2 generations when crossing

A

F1- offspring genotypes of first cross

F2- new offspring genotypes of previous offspring

18
Q

what is the genetic cross called

A

a punnet square

19
Q

what are the 4 blood types

A

A, B, O, AB

20
Q

Is blood group O dominant or recessive

A

recessive

therefore you need 2 blood group O alleles to be blood group O

21
Q

In a dihibrid cross why do we sometimes not get the expected ratio

A

sex linkage
autosomal linkage
epistasis

22
Q

what chromosomes do females have

A

XX

23
Q

what chromosomes do males have

A

XY

24
Q

What is sex linkage

A

when an allele is located on a sex chromosome
eg colour blindness
haemophilia

25
Q

in sex linkage does the Y chromosome on a male carry anything

A

no

26
Q

what is autosomal linkage

A

when the 2 genes are found on the same chromosome

Therefore inherited together

27
Q

what is the expected ratio when crossing 2 normal heterozygous individuals

A

9:3:3:1

28
Q

in epistasis what is the ratio for a dihribyrid cross involving a recessive allele

A

9:3:4

29
Q

in epistasis what is the ratio for a dihribyrid cross involving a dominant allele

A

12:3:1

30
Q

what is a gene pool

A

the complete range of alleles present in a population

31
Q

which hardy Weinberg equation predicts allele frequency

A

p + q = 1

32
Q

which hardy Weinberg equation predicts genotype and phenotype frequency

A

p2 + 2pq +q2 = 1

33
Q

in the hardy Weinberg equation what does p stand for

A

homozygous dominant

34
Q

in the hardy Weinberg equation what does q stand for

A

homozygous recessive

35
Q

in the hardy Weinberg equation what does pq stand for

A

heterozygous