Genetics Flashcards
(64 cards)
1
Q
What is biodiversity
A
variety of organisms in an ecosystem
2
Q
What is species diversity
A
number of different species within an area
3
Q
Benefits of high species diversity
A
- stable ecosystem
- each species is less likely to become extinct
4
Q
How to measure species diversity for an area
A
- species diversity index
- considers the number of different species and how many individuals there are for each species
- larger species diversity index = larger species diversity
5
Q
How does deforestation lower species diversity
A
- decreases plant species diversity
- less variety of habitats
- less variety of food sources
- decreases animal species diversity
6
Q
How does agriculture/farming reduce species diversity
A
- deforestation to make space for farm
- selectively breed plants and animals
- use pesticides to kill other species
7
Q
What is classification
A
placing organisms into groups
8
Q
What is hierarchical classification
A
large groups divided into smaller groups without overlap
9
Q
What is a species
A
a group of individuals with similar characteristics that can interbreed to produce fertile offspring
10
Q
Why are the offspring from 2 different species infertile
A
offspring will have an odd number of chromosomes so can’t perform meiosis, so cant’t produce gametes
11
Q
What is phylogenetic classification
A
species arranged into groups based on their evolutionary origins and relationships
12
Q
What are 3 ways of comparing relationships between different species
A
- DNA hybridisation; comparing DNA base sequence
- A A sequence; comparing A A sequence for the same protein
- Protein shape; comparing shape of same protein using immunological technique
13
Q
What is variation
A
difference in characteristics between organisms
14
Q
Two types of variation
A
- intraspecific; differences between organisms of the same species
- interspecific; differences between organisms of different species
15
Q
Causes of intraspecific variation
A
- genetic factors; same genes but different alleles
- environmental factors
16
Q
Causes of interspecific variation
A
- genetic; different genes and different alleles
- environmental factors
17
Q
Name two types of characteristics
A
- discontinuous
- continuous
18
Q
Properties of discontinuous characteristics
A
characteristics fall into certain groups with no overlap based on genetics only
19
Q
Properties of continuous characteristics
A
characteristics show a range determined by genetics and environment
20
Q
What is genetic diversity
A
number of different alleles of genes in a population
21
Q
Benefit of high genetic diversity
A
species able to adapt with changes in the environment
22
Q
What can reduce genetic diversity
A
small population size
23
Q
Describe the principles of natural selection
A
- random mutation can produce new alleles of a gene
- the new alleles may benefit the possessor, leading to an increased chance of survival and increased reproductive success
- the advantageous allele is passed onto the next generation
- over several generations, the new allele will increase in frequency in the population
24
Q
Name 2 types of selection
A
- stabilising
- directional
25
What is stabilising selection
when the environment favours those with the most common characteristic, so those on the extreme die out; common characteristic increases in proportion
26
What is directional selection
when the environment favours those with the uncommon, extreme characteristics; overtime, becomes the common characteristic
27
What is a gene
a section of DNA that codes for a protein
28
Components of a gene
- intron
- exon
29
Difference between intron and exon
exon codes for protein, intron doesn't
- intron = non-coding DNA
- exon = coding DNA
30
How does a gene code for protein
- gene is made of a sequence of bases
- each 3 bases code for 1 amino acid (triplet code)
- so the sequence of bases determines sequence of triplet codes which determine sequence of amino acids
31
Properties of triplet code
- degenerate; each amino acid has more than one triplet code
- non-overlapping; each base is only read once
32
How does a mutation lead to a non-functional enzyme
- change in base sequence
- change in sequence of triplet codes
- change in sequence of amino acids
- change in primary structure
- change in hydrogen, ionic and disulfide bonds
- change in tertiary structure
- change in active site shape
- substrate no longer complementary so no more ES complexes can be formed
33
How is a protein assembled
by transcription and translation
34
What is transcription
production of a single stranded complementary copy of a gene (mRNA)
35
What is translation
use sequence of codons on mRNA to assemble protein (tRNA brings in amino acids)
36
Define codon
a sequence of three bases on mRNA that codes for a specific amino acid
37
Define anticodon
a sequence of three bases at one end of a tRNA molecule that's specific to an mRNA codon
38
Name differences between DNA and RNA
- DNA, deoxyribose. RNA, ribose
- DNA, thymine. RNA, uracil
- DNA, double stranded. RNA, single stranded
39
What is mRNA (messenger RNA)
single stranded complementary copy of a gene which carries the code for assembling protein
40
What is tRNA (transfer RNA)
- single stranded RNA folded over into a clover shape held by hydrogen bonds between bases
- has amino acid on top
- has anticodon at bottom
- anticodon binds to complementary codons on mRNA
41
Describe the process of transcription
- DNA helicase breaks the hydrogen bonds between complementary bases
- two separate strands are formed, 1 coding, 1 template
- free RNA nucleotides align by complementary base pairing
- uracil is in place of thymine
- RNA polymerase joins adjacent nucleotides by phosphodiester bonds
- this leaves pre-mRNA
- its introns are removed by splicing to form mRNA
42
Differences between tRNA and mRNA
- tRNA is clover leaf shape, mRNA is linear
- tRNA has hydrogen bonds, mRNA doesn't
- tRNA has amino acid binding site, mRNA does not
- tRNA has anticodon, mRNA has codon
43
Describe the process of translation
- mRNA attaches to ribosomes on RER
- tRNA anticodons bind to complementary mRNA codons
- tRNA brings a specific amino acid
- amino acids join by peptide bonds with the use of ATP
- tRNA is released after amino acid joined to polypeptide
- ribosome moves along mRNA to form polypeptide
44
What does meiosis produce
4 genetically different cells (haploid)
45
Benefits of meiosis
produces gametes which will be used in sexual reproduction in animals and plants
46
Name the stages of meiosis
- interphase
- meiosis I
- meiosis II
- cytokinesis
47
What happens in interphase
- protein synthesis
- DNA replication
- organelle synthesis
48
What happens in meiosis I
- prophase I; DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
- metaphase I; homologous pair of chromosomes line up at centre of cell and attach to spindle fibre via the centromere
- anaphase I; spindle fibres pull, homologous pair of chromosomes separate to opposite poles via independent assortment
- telophase I; chromosomes uncoil, nucleus reforms (left with 2 nuclei)
49
What happens in meiosis II
- prophase II; DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
- metaphase II; chromosomes line up at centre of cell and attach to spindle fibres via centromere
- anaphase II; spindle fibres pull, centromere splits, sister chromatids move to opposite end of pole by independent assortment
- telophase II; chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei)
50
What happens in cytokinesis
cell separates into 4, each receives nucleus and cytoplasm
51
How does meiosis produce variation
- crossing over
- independent assortment
52
What is crossing over
homologous pair of chromosomes move towards each other and exchange genetic material
53
What is independent assortment
produces a mix of alleles from paternal and maternal chromosomes in a gamete
54
Define proteome of a cell
the full range of proteins a cell can produce
55
Define genome of a cell
the complete set of genes in a cell
56
What happens to DNA mass in meiosis
quarters
57
What happens to chromosome number in meiosis
halves
58
What is mutation
changes in sequence of nucleotides in a DNA molecule
59
Name 2 types of mutation
- chromosome mutation
- gene mutation
60
What causes mutation
random or due to mutagens
61
What is a chromosome mutation
- homologous pair of chromosomes don't separate in meiosis, so either inherit one extra or one less chromosome (non-disjunction)
- in plants, inherit more than one diploid set of chromosomes (polyploidy)
62
What is a gene mutation
a change in the base sequence of DNA
63
Name 3 types of gene mutation
- substitution; replace one base for another, changes one triplet code
- deletion; removing a base
- insertion; adding a base
64
What do insertion and deletion cause
frameshift mutations
