17: Inherited change

Question 1

Define a gene

Answer 1

A small section of DNA that codes for a specific protein

Question 2

Define a genotype

Answer 2

Genetic makeup of an organism

All the genes an animal can express

Question 3

Define a phenotype

Answer 3

Observable or biochemical characteristics of an organism

Can be altered by the environment

Question 4

What does an organisms genotype define?

Answer 4

The limits of the characteristics which an organism can develop
E.g lack of something could mean a person could not grow to max height

Question 5

Define locus

Answer 5

The position of a gene on a DNA molecule

Question 6

Define an allele

Answer 6

One of the different forms of a gene

Question 7

How many alleles can be present at one locus?

Answer 7

One

Question 8

How many copies of a gene are found in homologous chromosomes?

Answer 8

Two loci each carry one allele of a gene

Question 9

Define homozygous

Answer 9

When alleles on each of the homologous chromosomes are the same

Question 10

Define heterozygous

Answer 10

When alleles on each of the homologous chromosomes are different

Question 11

Define a dominant allele

Answer 11

Allele of a heterozygote that expresses itself in the phenotype

Question 12

Define a recessive allele

Answer 12

Allele of a heterozygote that does NOT expresses itself in the phenotype

Question 13

Define homozygous dominant

Answer 13

Homozygous organism with two dominant alleles

Question 14

Define homozygous recessive

Answer 14

Homozygous organism with two recessive alleles

Question 15

Define codominant

Answer 15

Two alleles which are both expressed in the phenotype

Question 16

When is an organism said to have multiple alleles?

Answer 16

Genes that have two allelic forms

Question 17

What can cause multiple alleles to occur?

Answer 17

Random mutations which occur over long periods of time

Question 18

Define monohybrid crossing

Answer 18

Crossing of one gene

Question 19

What is F0, F1, F2?

Answer 19

F0 - parent
F1 - offspring
F2 - offspring of F1 interbred

Question 20

Define the law of segregation

Answer 20

In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete

Question 21

Define a ratio

Answer 21

Measure of the relative size of two classes

Question 22

Why are results of genetic crosses rarely the same as predicted?

Answer 22

Predicted results are just predictions of what will occur, does not necessarily occur

Question 23

Define dihybrid inheritance

Answer 23

Crossing of two different genes located on different chromosomes, result is inherited

Question 24

What is the standard ratio caused by the breeding of two heterozygous organisms with dihybrid inheritance?

Answer 24

9:3:3:1

Question 25

What is the law of independent assortment

Answer 25

Each member of a pair of alleles may combine randomly with either of another pair

Question 26

What are the alleles present which determine blood group?

Answer 26

``` IA - produces antigen A on cell surface IB - produces antigen B on cell surface IO - does not produce any antigen on cell surface IA and IB are codominant IO is recessive to both ```

Question 27

What is the gene combination for blood types?

Answer 27

A - IAIA or IAIO B - IBIB or IBIO AB - IAIB O - IOIO

Question 28

Why might you not trust the dihybrid inheritance ratio 9:3:3:1?

Answer 28

Alleles are on the same chromosome therefore not independently assorted

Question 29

What does a 9:7 ratio suggest?

Answer 29

Not 3:1, but probably 9:3:3:1 which is common for a dihybrid

Question 30

What are the sex chromosomes?

Answer 30

23rd pair of chromosomes XX in females XY in males

Question 31

What is a Y chromosome?

Answer 31

A smaller and different shaped chromosome only found in males

Question 32

What gametes form from males and females?

Answer 32

Female - All gametes have single X chromosomes | Male - one has X chromosome other has Y

Question 33

What is a sex-linked gene?

Answer 33

Any gene that is carried on either the X or Y chromosome

Question 34

What does the extra length of the X chromosome mean?

Answer 34

The corresponding Y chromosome has no equivalent homologous portion Only one copy of a gene present in males

Question 35

How do recessive alleles on the non-homologous X chromosome change in frequency?

Answer 35

Recessive X chromosomes will appear more frequently as no homologous portion on Y chromosome could be dominant

Question 36

What is haemophilia?

Answer 36

Recessive allele on X chromosome which codes for a faulty protein that doesn't function Means blood cannot clot

Question 37

What is standard notation for looking at males and females in genetic diagrams?

Answer 37

Empty square - normal male Empty circle - normal female Filled shape - affected

Question 38

What is an autosome?

Answer 38

All chromosomes other than the sex chromosomes

Question 39

What are linked genes?

Answer 39

Any two genes that occur on the same chromosome are linked | Linked genes remain together in meiosis, pass onto gametes together

Question 40

Why are linked genes not separated in meiosis?

Answer 40

They do not segregate by independent assortment

Question 41

If the question presents you with the genotypes hhgg and HhGg, which alleles go together?

Answer 41

h always goes with g | Diagram is hg hg gametes crossed with HG hg gamets

Question 42

What is the difference between sex or autosomal linkage?

Answer 42

Sex linkage occurs when a gene is not found on the Y chromosome but is found on X Autosomal works on the non-sex chromosomes, so no Y chromosomes present

Question 43

What process in meiosis could cause varieties in ratios when sex-linked genes are crossing?

Answer 43

Crossing over may have occurred

Question 44

Define epistatis

Answer 44

The allele of one gene affects or masks the expression of another in the phenotype

Question 45

What is the classic example of epistatis?

Answer 45

Black, agouti, and albino mice

Question 46

What genes are found in the different colours of mice?

Answer 46

``` A - agouti a - black B - production of melanin b - no production of melanin If bb is present, the mouse is albino ```

Question 47

What is the standard format of a ratio?

Answer 47

A:1

Question 48

Why would some people not like to take part in testing?

Answer 48

Some embarrassed about | Cannot decide which phenotype is present, as it is subjective

Question 49

What shows that a phenotype is caused by a recessive allele?

Answer 49

Parents can be carriers but unaffected by the disease

Question 50

How many different gametes can be produced from Bb Cc Dd?

Answer 50

2^3 = 8 | Due to 1 allele from each pair

Question 51

How many antigen-determining alleles will be preset in a white blood cell?

Answer 51

2 - white blood cells are diploid cells

Question 52

What is the standard ratio when two AaBb mice mate?

Answer 52

9 - agouti 4 - albino 3 - black

Question 53

What are the steps in the chi squared test?

Answer 53

Observed (O) and Expected values (E) Sum of (O-E)^2 / E If this value is larger than the critical value, then there is enough data to reject H0

Question 54

When should the chi-squared test be used?

Answer 54

If: the data is in categories Sample size is large to be representative Data indicates absolute numbers

Question 55

If a question asks about a gene coding for enzymes with colours, how do you answer the question?

Answer 55

Gene X allows for the production of the enzyme | Enzyme causes chemical to made, giving the phenotype