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A-Level Biology- Y12 > 3.4.1-3.4.4 - Genetic information, variation and relationships > Flashcards

3.4.1-3.4.4 - Genetic information, variation and relationships Flashcards

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1
Q

Why is DNA described as a polymer?

A

Because a polymer is made from a molecule made up of lots smaller repeating monomers and DNA is made up of monomers called nucleotides.

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2
Q

Why is DNA referred to as a double helix?

A

the backbone structure consists of 2 helices twisted around each other

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3
Q

Explain how prokaryotic DNA differs to eukaryotic DNA

A

P is shorter and smaller.

Contains less non-coding DNA.

Not found in the nucleus- free floating

Not associated with histones

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4
Q

What are chromosomes?

A

Long strands of DNA. 23 pairs of chromosomes in a cell

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5
Q

Gene

A

A short section of DNA that code for one polypeptide

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6
Q

Allele

A

An alternative form of a gene.

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7
Q

Locus

A

Location of a gene on a chromosome

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8
Q

What are homologous chromosomes?

A

Two genetically similar chromosomes, one from each parent. Same structure but are not identical.

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9
Q

What are the 3 things that genetic code is?

A

Series of triplet codes

Universal

Non-overlapping

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10
Q

Degenerate DNA

A

A single amino acid can be coded for by more than one DNA triplet/codon.

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11
Q

What does genetic code provide the instructions for?

A

Protein synthesis

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12
Q

What is Protein synthesis a result of?

A

2 processes:

Transcription

Translation

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13
Q

Process of transcription

A

DNA helicase breaks the hydrogen bonds between 2 strands of DNA leaving 1 template strand. Free RNA nucleotides join up to exposed bases on DNA template strand. Weak hydrogen bonds form between them. RNA polymerase resynthesises backbone of mRNA by causing strong chemical bonds to form. mRNA is spliced. Hydrogen bonds between pre-mRNA and DNA are broken and DNA strands join together again.

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14
Q

What is splicing?

A

Pre-mRNA must be spliced before leaving the nucleus. Non-coding pieces of mRNA (introns) are removed. Only coding mRNA (exons) are left

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15
Q

What is specific about a ribosome?

A

Have 2 subunits.

Larger top is tRNA binding site.

Smaller bottom is the mRNA binding site

The mRNA moves through the ribosome subunits

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16
Q

Describe how translation leads to the production of a polypeptide (5 marks)

A

mRNA leaves the nucleus via the nuclear pores and enters the cytoplasm- it joins in between the 2 subunits of the ribosome

tRNA comes along with an amino acid and anti-codon. Anti-codon binds to complementary mRNA codon

Ribosome moves along to the next codon

Process of tRNA joining to mRNA repeats and amino acids join together using a peptide bonds

tRNA molecule moves away.

Process continues until a stop codon is reached

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17
Q

Mutations

A

a random error in gene replication that leads to a change. Spontaneous

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18
Q

Insertion

A

A base is inserted into the code and nucleotide added to the sequence

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19
Q

Deletion

A

A nucleotide is lost from the DNA sequence

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20
Q

Substitution

A

When one base is swapped for another

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21
Q

effects of mutations on transcription?

A

The triplet codes are transcribed into mRNA so a change in triplet code changes the mRNA sequence

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22
Q

Effects of mutation on translation?

A

Changes in mRNA changes amino acid order which changes the protein produced

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23
Q

Effects of mutation on genetic diversity?

A

More mutation=increased variation

Can decrease if an advantageous allele is favoured

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24
Q

Frame Shift

A

Every AA after the insertion or deletion will move one place

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25
Q

Mutagenic agent

A

A physical or chemical factor that changes genetic material and increases the frequency of a mutation occurring above natural rate

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26
Q

chromosomal mutation

A

Changes in the structure and number of whole chromosomes

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27
Q

2 types of chromosomal mutations

A

Polyploidy and non-disjunction

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28
Q

Polyploidy

A

Changes in number of whole chromosome. Cells have multiple sets of chromosomes

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29
Q

Non-disjunction

A

Homologous pairs fail to separate during meiosis so chromosome distribution is unequal

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30
Q

Mitosis Vs Meiosis- Role

A

Mitosis - growth/repair

Meiosis - gametes for sexual reproduction

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31
Q

Mitosis Vs Meiosis- amount of cell division

A

Mitosis- 1

Meiosis- 2

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32
Q

Mitosis Vs Meiosis- number of daughter cells

A

Mitosis: 2

Meiosis: 4

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33
Q

Mitosis Vs Meiosis- genetic composition

A

Mitosis- diploid

Meiosis- haploid

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34
Q

Mitosis Vs Meiosis- similarity to parent cells

A

Mitosis- identical

Meiosis- not identical

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35
Q

What is meiosis?

A

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

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36
Q

What happens during meiosis?

A

Meiosis 1- homologous pairs of chromosomes are separated. Two diploid cells are produced

Meiosis 2- sister chromatids are separated. Four haploid cells are produced

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37
Q

Genotype

A

genetic makeup of an organism

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38
Q

Phenotype

A

physical characteristics of an organism

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39
Q

Causes of genetic variation

A

sexual reproduction (meiosis) and mutations

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40
Q

How does meiosis result in genetic variation?

A

Crossing Over

Independent Assortment/Random Segregation

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41
Q

independent assortment

A

One of Mendel’s principles that states that genes for different traits can segregate independently during the formation of gametes. When homologous pairs line up, they do so randomly so each combination is changed

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42
Q

crossing over

A

Process in which homologous chromosomes exchange portions of their chromatids during meiosis. Sections have different alleles

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43
Q

Genetic Diversity

A

The total number of different alleles in a population as a result of mutations/meiosis

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44
Q

Explain how a mutation results in a change in characteristics

A

mutation occurs

-> Changes the DNA/Triplet code causing mRNA change

-> Changes the amino acid brought by tRNA

->Changes the primary and therefore tertiary structure

->Changes protein formed and it’s functions

->Increases genetic variation

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45
Q

Why is genetic diversity important?

A

Diverse gene pool gives a population more flexibility to survive in a changing environment. The more genetically diverse a population, the more ways it has to adapt. All genes may be the same but number of alleles may differ so genetic characteristics become vast

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46
Q

What does high genetic variation within a species mean?

A

large number of alleles

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47
Q

Advantages of high genetic diversity

A

Ability to adapt to a change in environment

More disease resistance within a population

Prevents extinction of wholes species

More availability of food and habitats

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48
Q

Disadvantages of high genetic diversity

A

Fewer organisms with characteristics suited for humans and fewer adapted organisms at a specific time

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49
Q

Natural selection

A

by Charles Darwin. Explanation as to why species have a wide variety of alleles- due to different reproductive successes that affect allele frequency within a gene pool

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50
Q

allele frequency

A

Number of times that an allele occurs in a gene pool

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51
Q

Gene pool

A

Combined genetic information (number of alleles) of all the members of a particular population

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52
Q

Differences between the reproductive success of individuals affect the allele frequency in a population, explain how. (6 marks)

A

Random allele mutation occurs.

This is advantageous for a proportion of the population.

They are more likely to reproduce because natural selection has enabled them to withstand certain conditions or environments.

They pass down the advantageous genes to offspring who will also be more likely to survive and reproduce due to adaptations.

This occurs at the expense of the less well adapted.

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53
Q

distribution curve

A

a graph that is constructed from the frequencies of the values of a variable

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54
Q

Normal distribution curve

A

a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer near the extremes.

55
Q

Why are most traits normally selected?

A

most characteristics are the result of multiple genes and eacch gene is affected by the environment.

Change in environment= change in the mean

56
Q

directional selection

A

Form of natural selection in which the entire curve moves; there has been a change in the environment causing mean to shift to one extreme

57
Q

stabilising selection

A

a type of natural selection in which genetic diversity decreases as the population stabilises on a particular trait value. selection acts against both extremes.

58
Q

Why is variation important?

A

The more variation within a species, the more likely it will survive and be able to adapt further

59
Q

Species

A

A group of similar organisms that can breed/combine genes and produce fertile and living offspring.

60
Q

Why do species become better adapted?

A

natural selection allows the further adaptation of species in 3 ways.

61
Q

Anatomical adaptations

A

Structural features of an organism’s body that increase its chance of survival.

e.g. sharp teeth or certain coloured fur.

62
Q

physiological adaptations

A

A chemical or physical event that takes place in the body of an organism to support its ability to survive and reproduce.

e.g. a camel’s hump getting hydrolysed to produce water

63
Q

behavioural adaptations

A

Ways an organism acts that increase its chance of survival

e.g. aggressive or protective behaviours

64
Q

What is a courtship display?

A

an adaptation focused on improving an organisms reproductive successes by increasing likelihood of selection by a mate

65
Q

examples of courtship displays

A

vocalisation, displays of strength or beauty, release of scents or chemicals, fighting or aggression

66
Q

What must courtship displays do?

A

increase the reproductive success of an individual

67
Q

how do courtship displays increase reproductive successes?

A

Enable an organism to recognise one of their own species- avoids crossbreeding which can create infertile offspring

Identifies if a mate is capable of breeding- prevents wasted energy and ensures a desired outcome

Forming pair bonds- ensures successful breeding and investment in raising offspring

Synchronised mating season- need to know they are in season and no energy will be wasted.

68
Q

What is a classification?

A

Organising living organisms into groups through a hierarchy of specific characteristics.

69
Q

Artificial classification

A

a method of classification based on analogous characteristics/what we can see

70
Q

analogous characteristics

A

physical features that have the same function. could have very different ancestors

71
Q

Phylogenetic classification

A

A type of classification that divides organisms into groups based on evolutionary relationships and homologous characteristics. It uses a hierarchy in which smaller groups are contained within larger groups, with no group overlap.

72
Q

homologous structures

A

similar structures that related species have inherited from a common ancestor

73
Q

Compare phylogenetic & artificial classification (4 marks)

A

AC: analogous characteristics, similar features, not based on evolution

PC: homologous characteristics, shared features derived from a common ancestor, based on evolutionary relationships

74
Q

Carl Linnaeus

A

Father of taxonomy- proposed phylogenetic classification based on ancestry and evolutionary relationship

75
Q

Key features of classification

A

arranges organisms into a hierachy, each group is called a taxon. From kingdom to species

76
Q

hierarchy

A

smaller groups within larger groups, no overlap between groups

77
Q

Binomial name

A

Scientific name of an organism, the first part of which designates the genus and the second part of which designates the species. E.g. Homo sapiens

78
Q

phylogenetic hierarchy

A

Life

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

(Let Donkey Kong Play Cards Over Four Gnomes Shirts)

79
Q

Why do we no longer use phylogenetic classification?

A

Based on mostly observable characteristics, subjective and influenced by the environment. We can find more accurate results using modern technology.

80
Q

Domains

A

Bacteria, Archaea, Eukarya

81
Q

Archea

A

Unicellular, small, DNA and genes, no murein or membrane bound organelle

82
Q

Bacteria

A

single-celled organisms that lack a nucleus; prokaryotes, free floating DNA, wall made from murein

83
Q

Eukaryote

A

A cell that contains a nucleus and membrane bound organelles, DNA associated with histones,

84
Q

What is a phylogenetic tree?

A

diagram that shows how species are related to each other through common ancestors/close relatives. Based on evolutionary history

85
Q

Evaluate the use of external features when constructing phylogenetic classification (5 marks)

A

+: easier to observe- anyone can do it

Doesn’t require any advanced equipment

-: patterns aren’t always clear

Interpretations are subjective

Genes can be polygenetic

May be result of different environments not genes

86
Q

How can genetic sequencing improve classification?

A

Genes can be compared and similarities can be identified. This is more accurate than observable characteristics

87
Q

What makes up the characteristics of an organism?

A

DNA-> Protein Structure -> characteristics of an organism

88
Q

Classification- DNA base sequence

A

Compare the order of nucleotides on the dna. Mutations lead to differences. More differences means fewer similarities so individuals are more distantly related

89
Q

Classification- mRNA sequences

A

mRNA is complementary to DNA.

Differences in mRNA = dna differences

More differences means more distantly related

90
Q

Classification- amino acid sequence in proteins

A

Differences in dna= diff in mRNA= differences in AA

UNLESS DEGENERATE

91
Q

How can we study genetic diversity without sequencing a genome?

A

DNA hybridisation or Biochemical analysis

92
Q

What is DNA hybridization?

A

Direct comparisons between the DNA sequences of different organisms based on knowledge of DNA structure

93
Q

How does DNA hybridisation occur?

A

DNA is heated so double strands separates into two complementary single strands - denaturation

The DNA is labelled using radioactive markers or labels

it is cooled and the complementary bases on each strands recombine - anneal

in cooling, the strands can bind to one another if hydrogen bonds form between complementary base pairs

94
Q

Which results of DNA hybridisation show similarities?

A

When you increase the temp, it should take a longer time to separate the 2 strands as

Higher temperature= more hydrogen bond= more similarities

95
Q

Biodiversity

A

The range and variety of genes, species and habitats within a particular region

96
Q

3 aspects of biodiversity

A

genetic diversity, species diversity, ecosystem diversity

97
Q

genetic diversity

A

The variety of genes or alleles posed by the individuals that make up 1 species

98
Q

species diversity

A

The number of different species and the number of individuals of each species within any 1 community

99
Q

ecosystem diversity

A

The range of different habitats within a particular area

100
Q

Abundance

A

The number of individuals of a specific species

101
Q

Species richness

A

the number of species in a given area at any time

102
Q

species diversity index

A

mathematical formula accounting for richness, abundance, and evenness. Suggested by Simpson

103
Q

Simpson’s Diversity Index

A

( N-(N-1) ) / ( total n (n-1) )

N = total number of organisms

n = number of individuals of each species

104
Q

Ecosystem stability

A

The higher the biodiversity the more stable the environment. If there is low biodiversity one significant change may kill all organisms which causes the ecosystem to crash

105
Q

Where do we study biodiversity?

A

In a field using quantitative methods to find abundance and distribution2 methods of studying biodiversity

106
Q

2 methods of studying biodiversity

A

Random sampling

Systematic sampling

107
Q

Quadrats

A

Comparison of two areas estimates a population size. A square grid. Can she frame quadrat or point quadrat

108
Q

Describe how you would estimate the population of dandelions in a field (4 marks)

A
  1. Random number generator=Random coordinates in a field

2.place quadrat

3.count number of organisms in sample

4.repeat at 10 coordinates

5.calc mean and times by area of field

109
Q

Transect

A

Measure the species distribution

110
Q

What is sampling bias?

A

Biased choices made by an investigator deliberately or unwillingly which makes the sample unrepresentative

111
Q

What should you consider when using a quadrat?

A

The size, the number of sample quadrats, the position of each quadrat

112
Q

Point quadrats

A

Frame containing a horizontal bar, long pins can be pushed through the bar, each species of plant that the pin touches is recorded

+:smaller organisms and smaller areas

-:tedious, hard to use and takes time

113
Q

What is systematic sampling?

A

studying in an ordered sampling frame. studies distribution

studies:gradual change across a habitat, transition within communities and if zonation is present

114
Q

types of transect

A

line and belt

115
Q

Line transect

A

a sampling method involving counting of species that touch the transect. String or tape used

116
Q

Belt transect

A

two parallel lines are marked along the ground and samples are taken of the area at specified points in between the lines.

117
Q

Evaluation of belt transect

A

+more consistent and bigger sample= more represenation

+more data

+finds abundance and range

-could be more time consuming

118
Q

Evaluation of line transect

A

+Quicker

+Easily shows species range along transect

+Clear view of how species change

-Harder to see range across a large range

-Less data collected

119
Q

What are transects used for?

A

They show how the distribution changes across an area. Show trends or patterns

120
Q

Using Transects - Method

A

1) Mark out a line in the area you want to study using a tape measure

2)Place quadrat at 0m and record species present

3)Repeat at equal intervals

4)Do the transect a few more times at similar locations and times so you can calculate the mean

121
Q

What does scientific research entail?

A

Observation, Hypothesis, Experimentation, Results analysis, further research

122
Q

Statistical testing

A

a mechanism for making quantitative decisions about a process

123
Q

Hypothesis

A

Statistical tests can be used to prove or disprove a null hypothesis

124
Q

Null hypothesis

A

the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.

125
Q

alternative hypothesis

A

The hypothesis that states there is a difference between two or more sets of data.

126
Q

Standard deviation

A

A statistical test. A measure of the width of the curve and indicates range. How much our data deviates from the mean

127
Q

Why is SD useful?

A

Tells you how much data deviates from the mean and determines how likely the results are due to chance

128
Q

correlation coefficient

A

a statistical index of the relationship between two things (from -1 to +1). Is there a significant correlation between 2 variables?

129
Q

How do you analyse statistical tests?

A

use the calculated value and degrees of freedom. Compare calculated value with the critical value in the table. Must be more than critical value (at 0.05) for there to be a significant difference.

130
Q

How do you calculate standard deviation?

A

Square root of the sum of measured value minus mean value squared divided by total number divided by 1

131
Q

degrees of freedom

A

The number of individual scores that can vary without changing the sample mean. Statistically written as ‘N-1’ where N represents the number of subjects.

132
Q

what does pearson correlation coefficient tell us?

A

if there is a significant difference, a relationship between 2 variables, if the correlation is positive or negative

133
Q

When would we use a two sample t test?

A

when you are looking for differences between measurements from different samples

134
Q

Steps to carry out a stats test

A
  1. Null hypothesis
  2. select appropriate stats test
  3. carry out calculation
  4. determine the degrees of freedom

5.Compare calculated value to critical value

  1. higher= reject null hypothesis

A-Level Biology- Y12 (14 decks)

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