Inheritence

Question 1

How can variation be created?

Answer 1

Genetically and environmentally

Question 2

What is aneuploidy?

Answer 2

Chromosome number is not an exact multiple of the haploid number for the organism.
Chromosomes and chromatids sometimes fail to separate properly
Trisomy seen in Down Syndrome is an example (3 copies of chromosome 21)

Question 3

What is polyploidy?

Answer 3

If a diploid and haploid gamete fuse the resulting zygote will be triploid.
Two diploid gametes would lead to a tetraploid zygote
Many cultivated plants are polyploid

Question 4

What is genotype?

Answer 4

Combinations of alleles inherited by an organism for a particular characteristic
Chemical composition, organisms DNA
Underlying genetic makeup, consists of physically visible and non-expressed alleles

Question 5

What is phenotype?

Answer 5

The observable characteristics, traits, expressed by an organism, determined by interaction between genetics and environment

Question 6

How is variation studied?

Answer 6

By observing a particular phenotype in a population, recording the different types of data present
If a large amount collected, frequencies of the different phenotypes can be calculated

Question 7

What is discontinuous variation?

Answer 7

Distinct categories into which individuals can be places
Tend to be qualitative: ability to roll tongue, blood groups
Controlled by a small number of genes with little environmental influence
Graphical representation is a bar graph

Question 8

What is polygenic inheritence?

Answer 8

Many genes involved in determining characteristic
Single characteristic controlled by alleles of two or more genes, results in continuous variation as range of phenotypes with smooth graduation from one extreme to other
Each gene may contribute small way, additive effect (height)
Greater loci number contributing to characteristic, more continuous variation (greater range)
Familiar 3:1 not seen

Question 9

What is continuous data?

Answer 9

No distinct categories
Tend to be qualitative, overlaps between categories
Controlled by a large number of genes with environmental influence
Height, mass
Graphical representation is line graph or frequency histogram

Question 10

What is chlorosis?

Answer 10

Plants coded to produce large amounts of chlorophyll, some have chlorosis meaning leaves look pale/yellow, as cells not producing normal chlorophyll amount

Question 11

How can lack of light effect chlorophyll production?

Answer 11

Plants turn off chlorophyll production in lower light to conserve resources, chlorosis occurs when plant gets no light

Question 12

How can mineral deficiencies effect chlorophyll production?

Answer 12

(Eg lack of iron/magnesium)
Iron needed as cofactor by some enzymes, magnesium in chlorophyll
If either are lacking, plant is unable to make chlorophyll and leaves become yellow

Question 13

How can virus infections effect chlorophyll production?

Answer 13

Interfere with metabolism of cells, yellowing in infected tissue as can no longer support chlorophyll synthesis

Question 14

What environmental factors may affect body mass?

Answer 14

Quality and amount of food consumed, exercise amount, presence of disease

Question 15

How can obesity be caused genetically?

Answer 15

Obese mice had mutated chromosome 7, causing pattern of fat distribution to be altered, working in conjunction with other genes, mice possessing mutation grow 35-50% fatter by middle age than normal mice

Question 16

What is a gamete?

Answer 16

Haploid sex cells for reproduction, carry half the genetic material
Male: sperm
Female: egg

Question 17

What are dominant genes?

Answer 17

Always expressed in an organism, over a recessive allele

Question 18

What are recessive genes?

Answer 18

Masked in presence of a dominant allele
To be expressed, must be two recessive alleles

Question 19

What is homozygous?

Answer 19

Refers to organism with two identical alleles for a specific gene (both dominant/both recessive)

Question 20

What is heterozygous?

Answer 20

Organism with two different alleles for a specific gene (dominant and recessive)

Question 21

What is F1 generation?

Answer 21

Refers to first filial generation of offspring from a cross between two parental organisms
Offspring from first cross

Question 22

What steps should be followed when completing a genetic cross?

Answer 22

State phenotype of both parents
State genotype of both parents
State gametes of each parent (BB = B and B)
Show crossing of each gamete
State proportion of each genotype produced (percentage/ratio)
State corresponding phenotype

Question 23

What is autosomal linkage?

Answer 23

Gene loci are on same chromosome, linked
Not able to undergo independent assortment as they are on the same chromosome: can only be inherited separately if crossing over happens between the two genes (less likely to occur the closer together they are)

Question 24

What is epistasis?

Answer 24

Two genes control a single characteristic, but one of the genes can mask the effect of the other
Similar to dominant and recessive, but epistasis applies to two genes at different loci, which affect the same characteristic
Reduces number of different phenotypes for characteristic, only be two or three phenotypes

Question 25

What is complementary epistasis?

Answer 25

Products from both genes are required for expression in the phenotype Often occurs in metabolic pathways controlled by enzymes Homozygous recessive alleles at either locus will result in one or both of the genes not being expressed, enzyme won't be reduced.

Question 26

What is antagonistic epistasis?

Answer 26

Alleles working against each other, one will mask the other Can be dominant/recessive

Question 27

What is dominant antagonistic epistasis?

Answer 27

Dominant allele at first locus prevents expression of allele at second locus First locus epistatic to second, called hypostatic

Question 28

What is recessive antagonistic epistasis?

Answer 28

When a recessive allele is epistatic to other genes when homozygous

Question 29

How is chi square used in inheritence?

Answer 29

Used to test if the different between observed and expected data is significant or due to chance Use chi square to see if ratio we seee is close enough to expected ratio (9:3:3:1) If difference too big, something else has influenced the population, as alleles have not been inherited as predicted

Question 30

What is the expected ratio for inheritence?

Answer 30

9:3:3:1

Question 31

What is natural selection?

Answer 31

Process by which organisms better suited to their environment tend to survive and produce more offspring

Question 32

When does stabilising selection occur?

Answer 32

Usually when there is no change to organisms environment

Question 33

Draw a graph to show stabilising selection

Answer 33

See cursive

Question 34

What is stabilising selection?

Answer 34

Natural selection leading to constancy in a population Intermediate phenotypes are favoured, extreme phenotypes are selected against Alleles for extreme phenotypes may be removed from the population. Stabilising selection reduced genetic variation within the population

Question 35

Give an example of stabilising selection

Answer 35

Birth weight, babies at extremes less likely to surive, too big and cannot leave birth canal, risks mothers life

Question 36

Draw a graph to show directional selection

Answer 36

See cursive

Question 37

When does directional selection occur?

Answer 37

Occurs due to a change in the organisms environment

Question 38

What is directional selection?

Answer 38

Type of natural selection that occurs when an environmental change favours a new phenotype and so results in a change in the population mean

Question 39

What are some examples of directional changes?

Answer 39

Turkeys on poultry farms Moths colour change during industrial revolution Horses

Question 40

When does genetic drift occur?

Answer 40

Occurs after genetic bottle neck or as a result of the founder effect

Question 41

What is genetic drift?

Answer 41

Variation in relative frequency of different genotypes in a small population, owing to chance disappearance of particular genes as individuals die/do not reproduce Chance, random events alter allele frequency and leads to reduction in genetic diversity

Question 42

Draw a diagram to show genetic bottlenecks

Answer 42

See cursive

Question 43

When does a genetic bottleneck occur?

Answer 43

When only a few individuals survive a random event (natural disaster, hunting etc), resulting in a shift in allele frequencies in the population

Question 44

What is a genetic bottleneck?

Answer 44

Event caused shift in allele frequencies Small population size facilitates inbreeding and genetic drift, decreasing genetic variation Some alleles lost from gene pool Genetic bottleneck is sharp reduction in size of population due to environmental events/human activity

Question 45

Give an example of a genetic bottleneck

Answer 45

Cheetahs, two bottle necks (ice age and last 100 years due to poaching) Less than 1% genetic variation, as if all cheetahs are identical twins

Question 46

Draw a diagram to show the founder effect

Answer 46

See cursive (NEED TO DO)

Question 47

What is the founder effect?

Answer 47

Reduced genetic diversity, results when a population is descended from a small number of colonising ancestors Small sample of original population establishes a new one Migrating individuals not genetically representative of parent population

Question 48

What do genetic drift and the founder effect not cause, but increase?

Answer 48

Do not cause mutations or emergence of harmful alleles, but contribute to increase in frequency of mutations and harmful alleles within resulting populations

Question 49

Give an example of the founder effect

Answer 49

Amish One of original 200 Amish founders had recessive allele for condition called Ellis van-Creveld syndrome, condition is type of dwarfism, people with syndrome have extra fingers and short limbs Amish population has higher cases of this syndrome than any other population

Question 50

What are population genetics?

Answer 50

Subfield of genetics that deals with genetic differences within and between populations, a part of evolutionary biology

Question 51

What factors will cause genotype frequency to stay the same?

Answer 51

-No selective advantage to any genotype so no selection -No mutations occuring -Population sufficiently large -All members will breed -Random mating -No migration in or out

Question 52

What is allotropic/geographical isolation?

Answer 52

Occuring within separate geographical areas that do not overlap

Question 53

What is speciation?

Answer 53

Process by which a new species is formed

Question 54

What is sympatric/reproductive isolation?

Answer 54

Occurring within same or overlapping geographical areas, takes place without geographical separation

Question 55

What is natural selection?

Answer 55

Environment provides selection pressure

Question 56

What is artificial selection?

Answer 56

Breeder chooses individual with desirable characteristics, actively excludes individuals with undesirable characteristics

Question 57

What are problems involved in artificial breeding?

Answer 57

Inbreeding Less genetic variation Less tolerant to change Increase in recessive genes Sometimes organisms are outbred to reduct frequency of recessive alleles and increase genetic variation