Inheritance

Question 1

Define:
Gene
Allele
Genotype
Phenotype
Monohybrid

Answer 1

Gene - inherited instruction which codes for a polypeptide
Allele - alternate form of a gene. Can arise from mutation
Genotype - genetic constitution of an organism that determines characteristics
Phenotype - observable traits of an organism
Monohybrid cross - cross in which the allele of only one gene are inherited

Question 2

Monohybrid inheritance

Answer 2

The inheritance of a characteristic controlled by a single gene.
Show the likely hood of different alleles of that gene being inherited from parents.

HH + hh = 100% Hh offspring

Hh + hh = 50/50 Hh hh

Question 3

Test cross

Answer 3

Determines if an organisms is homozygous dominant or heterozygous
Whether 2 genes are linked or not
Alway cross with homozygous recessive

Question 4

Co-dominance

Answer 4

• When alleles of a gene share dominance of characteristics - both are expressed in the phenotype
• example of diagram is capital letters with smaller letters as powers and as the characteristic

Question 5

Autosomal

Answer 5

Not sex chromosome

Question 6

ABO blood groups

Answer 6

IA + IB are dominant to I0 ??/

Question 7

Dihybrid cross

Answer 7

RrYy RRYY rRyY rryy
Inheritance of two genes with 2 different alleles each on different chromosomes

Independent segregation = alleles on different chromosomes so can pass into gametes in any combo

Question 8

9:3:3:1

Answer 8

DD : Dr : Dr : rr

Question 9

Autosomal linkage

Answer 9

• non sex chromosomes
• if genes are on same chromosome it is assumed they are inherited together (linked and no crossing over)
• stay together during independent segregation
• ## closer they are together, the closer they are linked

Question 10

Sex - linked inheritance

Answer 10

• genes on sex chromosomes
• female is XX
• males is XY
• Y is smaller so carries less genes
• some genes like faulty only carried by X so more likely inherited by male offspring due to only one X

Question 11

XX AND XY

Answer 11

XX = FEMALE
XY = MALE

Y = smaller so most genes on X. No homologous alleles present on Y.
Characteristics caused by recessive alleles have greater chance of appearing in males.

Question 12

Chi Squared

Answer 12

• assess if observed if significantly different from expected
• categorical raw values
• null hypothesis = no sig diff between O and E
• if calculated value is less than critical value then accept null.

Question 13

Epistasis

Answer 13

• polygenetic characteristics
• when alleles of one gene mask expression of another
• dominant = mask expression of alleles at second gene locus
• recessive - 2 recessive at one gene mask allies expression of another

Question 14

In genetic crosses, why are observed phenotypic ratios not the same as the expected ratios

Answer 14

-random fertilisation of gametes
-mutation/crossing over
-small sample size
-linked genes
-epistasis
-lethal genotypes

Question 15

Describe these phenotype frequencies:
- 1860, 580, 68,57

Answer 15

• larger numbers linked genes
• smaller numbers means a mutation has occurred which means they are random, not linked and not expected but onbserved.
• smaller numbers caused by crossing over

Question 16

Assumptions to why expected and observed are not the same?

Answer 16

• small sample size
• random fertilisation of gametes
• legthal genotypes

Question 17

Why is chi squared used

Answer 17

• to show if difference between observed and experceted is significant or not
• it’s CATEGORICAL DATA

Question 18

Diploid

Answer 18

Two sets of chromosomes so two alleles for each gene

Question 19

Gametes

Answer 19

Sex cells
Only one allele for each gene

Question 20

FOIL

Answer 20

First, outside, inside, last

Question 21

Phenotypic ratio

Answer 21

Ratio of different phenotypes in ratios
Can predict ratios in F1 and F2

Question 22

Causes of genetic variation

Answer 22

• crossing over
• random fertilisation
• independent segregation
• lethal alleles

Question 23

Locus

Answer 23

Position of gene on chromosome

Question 24

Recessive epistasis

Answer 24

Two copies of recesive epistasis allele masks or blocks expression of the other gene
9:3:4

Question 25

Dominant epistasis

Answer 25

When a dominant allele completely masks allel at 2nd locus
12:3:1

Question 26

Chi squared

Answer 26

X2= sum of (O-E)2/E

Question 27

Stats outcome

Answer 27

Equal or more = AND
Less = RSN