Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOLOGY A LEVEL > CHAPTER 20 - PATTERNS OF INHERITANCE AND VARIATION > Flashcards

CHAPTER 20 - PATTERNS OF INHERITANCE AND VARIATION Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

How can plants develop chlorosis

A

Lack of light
Mineral deficiencies
Virus infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an organisms genotype

A

The combination of alleles an organism inherits for a characteristic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is an organisms phenotype

A

Observable characteristics an organism has

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the terms for an organisms genotype

A

Homozygous and heterozygous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is continuous variation

A

A characteristic that can take any value within a range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is discontinuous variation

A

A characteristic that can only appear in specific discrete values

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the causes of continuous variation

A

Genetic and environmental

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the causes of discontinuous variation

A

Mostly genetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is continuous variation controlled by

A

Polygenes - controlled by a number of genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is discontinuous variation controlled by

A

One or two genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Examples of continuous variation

A

Leaf surface area
Animal mass
Skin colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Examples of discontinuous variation

A

Blood group
Albinism
Round and wrinkled pea shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

State the difference between a homozygous and heterozygous genotype

A

Homozygous – contains identical alleles of a gene.
Heterozygous – contains different alleles of a gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Explain the difference between the phenotype and genotype of an oak tree

A

Phenotype – the displayed characteristics of the oak tree e.g., how tall it grows (1);

Genotype – the
alleles present for each characteristic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Using named examples, state and explain the difference between continuous and discontinuous variation

A

Continuous – a characteristic which can take any value within a range

Discontinuous – a
characteristic which can take only specific values

continuous – affected by environmental and
genetic factors

discontinuous – affected by only genetic factors example of continuous
variation with explanation e.g., height, as genes affect potential height but diet can limit this
potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do you perform a genetic cross

A

State phenotype of both parents

State genotype of both parents

State gametes of each parents and circle letters

Use punnet square

State proportion of each genotype

State the corresponding phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is codominance

A

When two different alleles occur for a gene, but both of which are equally dominant

eg. AB blood group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is sex determined

A

23rd pair depends, if sperm cell contains X chromosome, then it is a female, if it contains Y chromosome, it is a male

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are sex linked genes

A

Genes that are carried on the sex chromosomes

Y is smaller than X so there is only one copy of a gene, so diseases can be more frequent on sex linked alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is haemophillia

A

A sex-linked genetic disorder, where blood clots extremely slowly due to the absence of a protein blood-clotting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is special about the phenotypes formed as a result of a gene which has codominant alleles

A

Codominant alleles are equally dominant

a heterozygous individual would display a phenotype
caused by the expression of both alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

State the difference between monogenic inheritance and dihybrid inheritance

A

Monogenetic inheritance is the study of the inheritance of one gene,

whereas dihybrid inheritance is
the study of the inheritance of two genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

State and explain why the offspring produced form a particular genetic cross may differ from the expected ratio

A

For example, genes are linked –
cannot be inherited independently

sample size is too small

unlikely to produce exact ratio
from small sample size, due to random nature of each individual outcome, crossing over of
chromosomes

new allele combinations created

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is autosomal linkage

A

Found on one of the pairs of chromosomes, and there is no independent assortment so they are inherited as one, unless they are separated by chiasmata

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are recombinant offspring

A

A different combination of alleles than either parent
(pg 531)

26
Q

How is recombination frequency calculated

A

RF = Number of recombinant offspring/total number of offspring

Less than 50% indicates a linkage
over 50 means there is no linkage

27
Q

What does the Chi squared test measure

A

Size of the difference between the results you got vs the results you expected to get

28
Q

What is epistasis

A

Interaction of genes on different loci, when one gene affects the expression of another
(pg 535 and 536)

29
Q

Horse coat colour is an example of epistasis. Two genes are involved. The different colours and the genotypes responsible are summarised here
G_ _ _ produces a grey horse
ggE_ produces a black horse
ggee produces a chestnut horse
Explain, giving your reasons, which form of epistasis this represents

A

Dominant epistasis

black allele / E, is dominant to, chestnut allele / e

grey allele / G, is
dominant to g

G (allele) is epistatic to E (allele)

E (allele) is hypostatic to G (allele)

30
Q

A biologist test crosses a plant that is heterozygous for the alleles Xx and Yy in order to see how far apart the gene loci are on a chromosome. The offspring of this cross contains 5.2% recombinant individuals.

State the difference between these alleles

Describe how the biologist could determine where a third gene with the alleles Zz is on the chromosome relative to Xx and Yy

Suggest why this sort of investigation is best carried out with genes that are relatively close to each other

A

A) 5.2 genetic map units

B) Cross Z,z with X,x and Z,z with Y,y (1);

idea that if Z locus closer to Y than X then order is X, Y, Z or
X, Z, Y

idea that if Z is more than 5.2 GMU from Y then order is X, Y, Z

idea that if Z is less
than 5.2 GMU from X then order is X, Z, Y

C) Genes further apart more likely to cross more than once

(this will) cancel previous cross

so
incorrect recombination frequency

31
Q

What is the gene pool

A

The sum total of all the genes in a population at any given time

32
Q

What is allele frequency

A

The relative frequency of a particular allele

33
Q

What is Hardy-Weinberg principle states

A

In a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next and there will be no evolution

34
Q

How do you calculate allele frequency

A

p+q=1

35
Q

How is the hardy weinberg principle expressed

A

p^2 + 2pq + q^2 = 1

36
Q

What are the factors affecting evolution

A

Mutation is necessary for the existence of different alleles

Sexual selection

Gene flow

Genetic drift

Natural selection

37
Q

What are the limiting factors which limit or decrease population size

A

Density-dependent factors eg. competition, predation, parasitism, communicable disease

Density-independent factors eg. climate change, natural disasters, human activities

38
Q

What is a genetic bottleneck

A

A natural disaster or epidemic (or change in environment) that can drastically reduce a population, reducing gene pool
(pg 541)

39
Q

What is the founder effect

A

the reduction in genomic variability that occurs when a small group of individuals becomes separated from a larger population

40
Q

What is stabilising selection

A

The average is selected for (positive selection) and the extremes are selected against, increasing frequency of average alleles
eg. baby weight

41
Q

What is directional selection

A

When there is a change in the environment and the most occurring phenotype is no longer advantageous

leading to organisms with less common alleles are positively selected
eg. peppered moth colour

42
Q

What is disruptive selection

A

Extremes are selected for and the norm is selected against, opposite to stabilising selection
eg. Darwins finches (pg 543/544)

43
Q

Explain why Evolution does not occur within single organisms but groups of organisms

A

Evolution is change in allele frequency

alleles do not change within organism

single organisms do not adapt

44
Q

Around the world, humans choose their partners from right of reasons. Explain why this might affect any conclusions about human evolution drawn, using the hardy Weinberg principle.

A

The Hardy–Weinberg principle assumes a stable, isolated breeding population of diploid organisms with random mating, no mutations, and no selection pressure

Because people choose their partners or have them chosen for them by their parents, mating is not random

Any conclusions based on Hardy–Weinberg principles will not, therefore, be valid, because the equilibrium only holds in ideal conditions

individuals do not reproduce with visibly similar organisms

45
Q

Eukaryotic organisms have large quantities of non-coding DNA, whereas most prokaryotic organisms have very little. Suggest with reference to the different forms of reproduction in eukaryotes and prokaryotes why eukaryotes may have evolved to have more non-coding DNA

A

Sexual reproduction in eukaryotes and asexual reproduction in prokaryotes

(involves) meiosis

crossing over

idea that non-coding regions of DNA reduce disruption of genes (during crossing over)

46
Q

What are the events that lead to speciation

A

Members of a population became isolated and no longer interbreed

Allele within the groups continue to undergo random mutations

Accumulations of mutations and changes in allele frequencies over many generations eventually lead to a change of phenotype

47
Q

What is allopatric speciation

A

When some members of a population are separated from the rest of the group by a physical barrier such as a river or sea
(pg 546)

48
Q

What is adaptive radiation

A

Rapid organism diversification takes place

49
Q

What is sympatric speciation

A

Speciation that occurs within populations that share the same habitat

It can occur when members of two different species into breed and form a fertile offspring, which forms a hybrid, but will have a different number of chromosomes to the parent and may no longer be able to interbreed, so it is reproductively isolated and stops gene flow
(pg 547)

50
Q

What are prezygotic reproductive barriers

A

Prevent fertilisation and formation of a zygote

51
Q

What are postzygotic reproductive barriers

A

Reduces the viability or reproductive potential of offspring eg. by hybridisation

52
Q

What is polymorphic

A

When there are more than one distinct phenotype in a population

53
Q

What is artificial selection/selective breeding

A

Natural selection except for the nature of the pressure applied

farmers/breeders breed animals with desirable characteristics

54
Q

What is inbreeding

A

The breeding of closely related individuals

55
Q

What are some problems with inbreeding

A

Limiting gene pool - reducing genetic diversity and chances of adapting to environment

Genetic disorders caused by recessive alleles are more prevalent - breeding partners likely to have same recessive alleles

56
Q

What are gene banks used for

A

Storing biological samples

Used to increase genetic diversity by outbreeding

57
Q

Describe with examples, the difference between pre-zygotic and post-zygotic reproductive barriers

A

Pre-zygotic reproductive isolation before fertilisation stage

e.g., geographical, behavioural, seasonal, anatomical

post-zygotic reproductive isolation after fertilisation

e.g., zygote not viable, offspring infertile

58
Q

A small population of adders in Sweden underwent inbreeding depression and farming activities, isolated them from other other populations. The numbers of stillborn and formed offspring increased as compared to the original population. Research is introduce atoms from other population, and the isolated population recovered and produce a high proportion of viable offspring.

Name, the type of breeding carried out by the researches

Explain how this type of breathing reduces the problems caused by inbreeding

A

Outbreeding

Introduces new alleles, which
can be beneficial, Increasing (genetic) variation

(population) more able to cope with changes in environment / new selection pressures

number of homozygous recessive loci reduced (over time)

59
Q

Discuss what variation within a species has to be present for speciation to occur

A

(Isolated) organisms exposed to different environments

(so) different selection pressures

variation means that a wide range of alleles is present

(in different environments) different alleles selected for

different changes in allele frequency leads to formation of different species

60
Q

Allopatric speciation is considered by most biologist to be the most common way in which new species, evolve

Outline the differences between sympatric, speciation, and allopatric speciation, and suggest why some biologist thinks sympatric speciation is a rare event

A

Sympatric speciation occurs within same habitat

selection pressures the same for all

allopatric speciation occurs within isolated groups

isolated groups (may have) different selection pressures

(some) gene flow in sympatric speciation and no gene flow in allopatric speciation

organisms not isolated in sympatric speciation so gene flow is still possible

BIOLOGY A LEVEL (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions