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Biology revision unit 2 Flashcards

KK1,KK2,KK3,KK4,KK5. Chromosomes, genotypes and phenotypes, patterns of inheritance, reproductive strategies, adaptations and diversity

1
Q

Draw DNA polymer structure

A

Phosphates = circle (first bit of structure)
Deoxyribose sugar =(hexagon in the middle)
Nitrogenous base = (last 2 hexagons)

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2
Q

What are the 4 nitrogenous bases found in DNA

A

Adenine
Guanine
Thymine
Cytosine

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3
Q

What bases bond together

A

Adenine and Thymine
Guanine and Cytosine

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4
Q

How is DNA packaged

A

Phosphates link together neighboring nucleotides together to form one-half of the double-stranded DNA molecule

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5
Q

How is DNA packaged into chromosomes

A

Double-stranded
Histones organize the DNA into coiled structures

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6
Q

Definition of Gene

A

A section of DNA that codes for a particular protein

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7
Q

Definition of Allele

A

Versions of a gene that code for variations of the phenotypic trait

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8
Q

Definition of Genome

A

All genetic material that is in a haploid set of chromosomes

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9
Q

Eg of how an allele is a different version of the same gene

A

E.g.: coat color in a rabbit. One allele may code for a grey colour and one may code for a black coat. Both for the same gene just a variation

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10
Q

Gene Locus definition

A

The position of a gene on a chromosome

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11
Q

Draw a eukaryotic chromosome and label its structure

A

Must have:
- Homologous Chromosomes
- Gene Locus
- Sister chromatids
- Centromere

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12
Q

3 features of Homologous chromosomes (what makes them homologous)

A

3 of the following:
-Length/Size
-Centromere position
-Same Genes at the same location
-Banding Pattern

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13
Q

What are the autosomal and sex chromosomes (what numbered pairs are what)

A

1-22nd pair are autosomal
23rd pair are sex chromosomes

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14
Q

Why do chromosomes come in homologous pairs

A

one is from the mother and one is from the father. Each gives one chromosome because of cell division. Makes sure the offspring have all the genes and the correct amount of DNA

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15
Q

How is a Karyotype created

A

Taken a photo of cells during the start of cell division when all the chromosomes are condensed
Steps are:
-Find a cell in metaphase
-Extract chromosomes
-take photograph
-Pair and sort

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16
Q

Relationship between chromosome size and number of genes

A

The bigger/larger the size of the chromosome the larger number of genes are found on them

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17
Q

What are 2 things you can find out from a Karyotype

A

Abnormalities in number of chromosomes
Sex of individual

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18
Q

What are the chromosomal abnormalities in a person with Down syndrome

A

Trisomy 21 (extra chromosome on 21)

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19
Q

What are the chromosomal abnormalities in a person with Klinefleders syndrome

A

XXY
(extra x)

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20
Q

What are the chromosomal abnormalities in a person with Turner syndrome

A

x
no y

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21
Q

Haploid cell and diploid cell difference

A

diploid cells contain two complete sets. Haploid organisms, on the other hand, only contain one complete chromosome set.

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22
Q

2 stages of Meiosis

A

Meiosis I and Meiosis II

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23
Q

Explain what occurs at each stage of meiosis I and II

A

Prophase 1= Chromosomes condense, crossing over occurs
Metaphase 1= Homologous chromosomes line up on cell equator
Anaphase 1=Homologous cells are seperated
Telephase 1=new nucelus are formed
Prophase 2=Chromosomes condense and nucleur envelope breaks down
Metaphase 2=Sister chromatids (chromsomes) line up on equator
Anaphase 2=Sister chromatids are sperated
Telephase 2=Nucleur envelope formed

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24
Q

define haploid

A

Haploid describes a cell that contains a single set of chromosomes

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25
Q

define diploid

A

the presence of two complete sets of chromosomes in an organism’s cells, with each parent contributing a chromosome to each pair.

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26
Q

Explain how genetic variation is created in chromosomes

A

Independant assortment- the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene. Therefore increases amount combinations of alleles the gamete can recieve and therefore increases genetic variation
Crossing over-when genetic material is swapped between two chromosomes. (When homologous chromosomes come together to form tetrads, the arms of the chromatids can swap at random, creating many more possibilities for genetic variation of the gametes.)

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27
Q

Genotype definition

A

Genetic make up which determines the phenotype
Combination of alleles determine for a gene

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28
Q

Phenotype definition

A

What is expressed, observable characteristics
* Controlled by both the genotype and the environment

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29
Q

What are the factors that determine a phenotype

A

-Genotype
-Epigenetics
-enviroment

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30
Q

What is the combination of Alleles in a Heterozygous genotype

A

Aa (dominant and recessive)

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31
Q

What is the combination of Alleles in a homozygous genotype

A

aa or AA (both dominant alleles or both recessive alleles)

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32
Q

How will a genotype with complete dominance (dominant or recessive) affect the expression of the phenotype

A

1 Dominant allele present means that the dominant allele will be expressed
2 recessive alleles required for the recessive phenotype to be shown

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33
Q

How will a genotype with co-dominance affect the expression of the phenotype

A

AA = dominant trait
Aa = both traits expressed
aa-recessive trait (not really recessive but)

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34
Q

How will a genotype with incomplete dominance affect the expression of the phenotype

A

AA=dominant
Aa=intermediate of both traits
aa= recessive

35
Q

compare co domiance and incomplete dominance

A

co-dominance = both traits are expressed fully
incomplete = an intermediate of the traits is expressed
What they have in common = both express some version of both alleles

36
Q

define epigenetics

A

the study of changes in an organism (modification of gene expression)

37
Q

What does an epigenetic factor do

A

Change how DNA is packaged

38
Q

What is an example of a epigenetic factor to do with lifestyle

A

diet, obesity, physical activity, tobacco smoking, alcohol consumption, environmental pollutants, psychological stress

39
Q

What is methylation

A

the addition of a methyl group to a cytosine base

40
Q

what does methylation do

A

stops the gene from being transcribed (stops transcription proteins from binding)

41
Q

What does a shaded square stand for in a pedigree

A

an affected male

42
Q

What does a shaded circle stand for in a pedigree

A

an affected female

43
Q

What does a unshaded square stand for in a pedigree

A

an unaffected male

44
Q

What does a unshaded circle stand for in a pedigree

A

an unaffected female

45
Q

what does the line between a unrelated male and female mean in a pedigree

A

marriage line

46
Q

what does a half shaded circle or square mean in a pedigree

A

a carrier

47
Q

Brown eyes are a dominant eye-color allele and blue eyes are recessive. A brown-eyed woman
whose father had blue eyes and whose mother had brown eyes marries a brown-eyed man whose
parents are also brown-eyed. They have a son who is blue-eyed.
Draw a pedigree (info above) showing all four grandparents, the two parents, and the son. Indicate
each individuals possible genotypes.

A

work it out

48
Q

define the law of segregation

A

The Law of Segregation states that alleles segregate randomly into gametes: When gametes are formed, each allele of one parent segregates randomly into the gametes, such that half of the parent’s gametes carry each allele

49
Q

What is the genotypic and phenotypic ratio of a monohybrid cross between 2 heterozygous individuals(trait shows complete dominance)

A

genotypic = 1:2:1
phenotypic =3:1

50
Q

What is the genotypic and phenotypic ratio of a monohybrid cross between a heterozygous individual and a homozygous dominant(trait shows complete dominance)

A

Genotypic = 1:1
Phenotypic = all dominant

51
Q

What is the genotypic and phenotypic ratio of a monohybrid cross between a heterozygous individual and a homozygous recessive(trait shows complete dominance)

A

genotypic=1:1
phenotypic = 1:1

52
Q

What is the genotypic and phenotypic ratio of a monohybrid cross between a homozygous dominant individual and a homozygous recessive(trait shows complete dominance)

A

Genotypic= all heterozygous
phenotypic =.all dominant

53
Q

What is the genotypic and phenotypic ratio of a monohybrid cross between 2 heterozygous individuals(trait shows incomplete dominance)

A

genotypic = 1:2:1
phenotypic = 1:2:1

54
Q

what is the genotypic and phenotypic ratio of a monohybrid cross between a carrier mother of a x linked recessive trait and a unaffected father

A

genotypic = 1:1:1:1(Dom female, carrier female, dom male, affected male)
phenotypic =2:1:1

55
Q

what is the genotypic and phenotypic ratio of a monohybrid cross between a unaffected mother of a x linked recessive trait and a affected father

A

genotypic =1:1
phenotypic = 1:1

56
Q

what is the genotypic and phenotypic ratio of a monohybrid cross between a unaffected mother of a x linked dominant trait and an affected father

A

genotypic = 1:1
Phenotypic =1:1

57
Q

Draw a monohybrid cross between 2 heterozygous individuals. The recessive genotype is lethal.
What is the phenotypic and genotypic ratio

A

genotypic ratio = 2:1
phenotypic ratio = all domiant

58
Q

Draw a monohybrid cross between 2 heterozygous individuals. having 2 of the dominant alleles is lethal.
What is the phenotypic and genotypic ratio

A

g=2:1
p= 2:1

59
Q

what is a monohybrid test cross

A

a cross between an individual showing the dominant allele and an individual showing the recessive allele

60
Q

what is the purpose of a monohybrid test cross

A

to find out the genotype of the individual showing the dominant phenotype

61
Q

Explain how two genes will independently assort or be linked over generations.

A

Genes on separate chromosomes assort independently because of the random orientation of homologous chromosome pairs during meiosis.
Genes on the same chromosome will independently assort together meaning they are inherited together. Can only be separated by crossing over but it is rare.

62
Q

How is a dihybrid cross different from a monohybrid cross

A

A dihybrid cross looks at the probability of inheritance of 2 genes not just one unlike a monohybrid cross

63
Q

determine the possible gamete combinations of an individual with the genotype AABb

A

AB
Ab
AB
Ab

64
Q

determine the possible gamete combinations of an individual with the genotype AaBb

A

AB
Ab
aB
ab

65
Q

determine the possible gamete combinations of an individual with the genotype aaBb

A

aB
ab
aB
ab

66
Q

what is the phenotypic ratio in a dihybrid cross with 2 heterozygous individuals for both traits

A

9:3:3:1

67
Q

If 2 genes are linked. what is the genotypic ratio/phenotypic

A

usually around 49:1:1:49

68
Q

What are the genotypes of the offspring called when linked genes are separated due to crossing over

A

recombinants

69
Q

What does the word parthenogenesis mean

A

Virgin birth

70
Q

what is pathogenesis

A

Reproduction without fertilisation. Egg is produced by mitosis.

71
Q

What is facultative pathogenesis

A

pathogenesis used when required i.e. when there is a lack of males.

72
Q

What is Obligate pathogenesis

A

Are an all female population (used always)

73
Q

What is budding

A

A small part of the parent body separates from the rest and develops into a new individual, which is smaller than the parent.
Note: This new individual may remain attached as part of the colony, or the bud may constrict at its point of attachment and be released as an independent organism.

74
Q

What is fragmentation

A

The organism spontaneously divides into
fragments. Each fragment develops into a mature, full grown individual identical to the original organism.

75
Q

eg: of an organism that uses pathogenesis

A

Sharks, Komodo dragons

76
Q

eg: of an organism that uses fragmentation

A

flatworms, starfish

77
Q

eg: of an organism that uses budding

A

yeast, hydra

78
Q

Name the stages of binary fission in prokaryotes

A
  1. Replication: of circular DNA
  2. Attachment: of the two circular DNA
    molecules to the poles of the plasma
    membrane.
  3. Lengthening: of the cell
  4. Division: into two cells by constriction
    across the middle of the cell.
79
Q

Advantage of vegetative propagation

A

-helps preserve the characters of the plants through successive generations
- they do not need to produce flowers,pollen, or seeds (processes with large energy costs).

79
Q

Definition of vegetative propagation

A

The process by which new individuals arise without the production of seeds or spores

80
Q

Name 4 types of vegetative propagation

A

Tubers, bulb, rhizomes, cuttings, grafting.

81
Q

Advantages of asexual reproduction

A

-can reproduce quickly
- no energy expended finding a mate
- don’t rely on other organisms
-well suited to environment
-able to colonise cleared areas quickly

82
Q

Disadvantages of asexual reproduction

A

-Lack of genetic variation
-pressure on availability of resources
-if conditions change, entire population can be lost

83
Q

Explain why some organisms use both sexual and asexual reproduction

A

So that they can reproduce in the way that most suits the current environmental conditions

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