genetics, populations, evolution and ecosystems- topic 7

Question 1

Genotype

Answer 1

Genetic constitution of an organism, determines variation

Question 2

phenotype

Answer 2

Observable characteristic; expression of genotype and affected by the environment

Question 3

gene

Answer 3

Length of DNA that codes for a polypeptide/protein/rRNA
or tRNA

Question 4

Locus

Answer 4

Position of a gene on a piece of DNA or chromosome

Question 5

allele

Answer 5

different forms of a gene

Question 6

Homologous chromosome

Answer 6

Pair of chromosomes, one maternal and one paternal in origin. They contain the same genes at the same loci, although alleles can vary

Question 7

Homozygous

Answer 7

Identical alleles at the same locus on homologous chromosomes

Question 8

heterozygous

Answer 8

different alleles at the same locus on homologous chromosomes

Question 9

dominant allele

Answer 9

Allele that is expressed in the phenotype of an organism. Only 1 copy is needed. It masks any recessive allele

Question 10

recessive allele

Answer 10

Only expressed in the phenotype when both alleles present are recessive. Not expressed if dominant allele present

Question 11

codominant alleles

Answer 11

In a heterozygous genotype, both forms of the allele are expressed resulting in a phenotype that is a mixture

Question 12

multiple alleles

Answer 12

Three or more allelic forms of which only two can exist in a diploid individual at any one time, e.g. ABO blood groups

Question 13

Monohybrid inheritance

Answer 13

Inheritance of a single pair of alleles e.g. Bb or Gg

Question 14

dihybrid crosses

Answer 14

Dihybrid crosses are those where we consider the inheritance of two characteristics at the same time. For example brown hair and blue eyes together, so a person could be genotype HhEe

Question 15

dihybrid cross 2 heterozygotes ratio

Answer 15

9:3:3:1

Question 16

gametes for HhEe

Answer 16

HE, He, hE, he

Question 17

Gametes for HHEE

Answer 17

HE

Question 18

gametes for hhee

Answer 18

he

Question 19

what can be used to determine deviation between observed and expected values

Answer 19

chi squared

Question 20

why can chi squared be used for codominance

Answer 20

because the data is discrete

Question 21

homozygous dominant

Answer 21

2 dominant alleles

Question 22

homozygous recessive

Answer 22

2 recessive alleles

Question 23

how are codominant alleles shown in a punnet square

Answer 23

C^allele letter eg:C^w

Question 24

how are blood group alleles shown

Answer 24

I^blood group eg: I^A

Question 25

male sex chromosomes (humans)

Answer 25

XY

Question 26

female sex chromosomes (humans)

Answer 26

XX

Question 27

are X linked conditions always dominant or recessive

Answer 27

recessive (expressed in males as no equivalent genes on Y)

Question 28

do sex linked disorders predominantly affect men or women in humans, why

Answer 28

men as there are no equivalent genes on the Y chromosome to prevent the recessive allele from being expressed

Question 29

How are sex linked chromosomes shown

Answer 29

X^allele letter or Y^allele letter

Question 30

autosome

Answer 30

any chromosome which is not a sex chromosome

Question 31

autosomal linkage

Answer 31

2 or more genes are carried on the same chromosomes. Therefore dominant alleles are paired together and recessive alleles are paired together

Question 32

reason for autosomally linked chromosomes to not remain together

Answer 32

crossing over

Question 33

crossing over

Answer 33

process where a chromatid breaks during meiosis (prophase 1) and re-joins to the chromatid of its homologous chromosome so that their alleles are exchanged

Question 34

epistasis

Answer 34

when the allele of one gene affects or masks the expression of another in the phenotype. usually happens with colours eg: colour arrangement being masked by being albino

Question 35

gene pool

Answer 35

all the alleles of all the genes of all the individuals in a population of a single species at a given time. It includes both genes that are expressed, and those that are not.

Question 36

hardy weinberg principle

Answer 36

predicts that the frequency or proportion of alleles (of a particular gene) will stay constant from one generation to the next

Question 37

assumptions of hardy weinberg principle

Answer 37

no selection, no mutation, no migration, large population, random mating

Question 38

p + q=

Answer 38

1

Question 39

p=

Answer 39

dominant

Question 40

q=

Answer 40

recessive

Question 41

p^2 + 2pq +q^2=

Answer 41

1