Inheritance, Variation and Evolution Flashcards
1
Q
Types of reproduction
A
- sexual
- asexual
2
Q
Sexual reproduction
A
Genetic information from 2 organisms (father + mother) fusing to produce offspring genetically different from parents
3
Q
What do the mother and father produce in sexual reproduction
A
Gametes
4
Q
Gametes
A
Sex cells
5
Q
Male gamete
A
Sperm cell
6
Q
Female gamete
A
Egg cell
7
Q
How many chromosomes in a human gamete
A
23
8
Q
Fertilisation
A
Egg from mother + sperm from father fuse together to form a zygote (fertilised egg) with full number of chromosomes (46)
9
Q
What kind of reproduction do flowering plants use
A
Sexual
10
Q
How do flowering plants reproduce
A
Pollen (containing male gametes) from a plant carried to another plant’s egg cell
11
Q
Why does sexual reproduction lead to variety in offspring
A
There is mixing of genetic information
12
Q
Asexual reproduction
A
1 parent cell divides by mitosis to form 2 genetically identical cells (to each other and parent cell) - clone
13
Q
What organisms reproduce asexually
A
- bacteria
- some plants
- some animals
14
Q
What does meiosis produce
A
Gametes
15
Q
How many cell divisions happen in meisosis
A
2 rounds
16
Q
Where does meiosis happen in humans
A
Reproductive organs - ovaries + testes
17
Q
Meiosis STAGE 1
A
- before division
- cell duplicates genetic info
- 2 armed chromosomes formed - 1 arm exact copy of other arm
- chromosomes arrange into pairs
18
Q
Meiosis STAGE 2
A
- first division
- chromosomes line up in centre of cell
- pairs pulled apart
- each new cell has 1 copy of each chromosome
- some of father’s + mother’s chromosomes in each cell
19
Q
Meiosis STAGE 3
A
- second division
- chromosomes line up in centre of cell
- arms pulled apart
- 4 gametes - 23 chromosomes in each
- gametes genetically different from other as chromosomes shuffled up during meiosis - each gamete gets half at random
20
Q
What happens after gamete fusion
A
- resulting cell divides by mitosis many times to produce copies of itself in embryo
- embryo develops - cells differentiate, specialised cells eventually make up whole organism
21
Q
Chromosomes
A
Long molecules of DNA
22
Q
How are chromosomes usually found
A
In pairs
23
Q
What does DNA stand for
A
deoxyribonucleuic acid
24
Q
DNA
A
Chemical all genetic material is made up of
25
What does DNA contain
Coded information - instructions to put organism together and make it work
26
Where is DNA found
Nucleus of animal + plant cells
27
Structure of DNA
Polymer made up of 2 strands coiled together in shape of double helix
28
Gene
Small section of DNA that codes for a particular sequence of amino acids, put together to make a specific protein
29
How do genes code
Tell cells what order to put amino acids together in
30
How many amino acids are used to make proteins in humans
20
31
How many proteins are found in humans
Thousands
32
What determines what type of cell a cell will be
What proteins it produces - determined by DNA
33
Genome
Entire set of genetic material in organism
34
Has the complete human genome been worked out
Yes
35
How is understanding the human genome important for medicine
- scientists can identify genomes linked to different types of disease
- know genes linked to inherited disorders - could develop effective treatments
36
How can understanding human genome be used to trace past human migration patterns
- modern humans descended from common ancestor from Africa
- as different populations migrated away from Africa, developed tiny differences in their genome
- investigate differences - work out when new populations split off + route they took
37
Which chromosomes determine your sex
23rd pair
38
Types of 23rd chromosome pair
- XY
- XX
39
XY chromosome
Y chromosome causes male characteristics
40
XX chromosomes
XX combination allows female characteristics to develop
41
Probability of sperm getting X/Y chromosome in meiosis
50%
42
What chromosome do all egg cells have
X
43
How to find probability of getting a boy or girl
Draw a genetic diagram
44
What are genetic diagrams
Models used to show all possible outcomes when different genes/chromosomes crossed together
45
Types of genetic diagrams
- Punnett square
- genetic cross
- family trees
46
How to use Punnett square to find probability of having boy or girl
- put possible gametes from one parent down side, other parent's at top
- male parent - sperm with X chromosome OR sperm with Y chromosome
- female parent
- egg with X chromosome OR egg with Y chromosome
- fill in boxes to make pairs of letters
47
How to use genetic cross diagram to find probability of having boy or girl
- parent chromosome pairs at top - XX + XY
- middle circles show possible gametes - X X X Y
- crossed lines show all ways X and Y chromosomes could combine
- possible combinations of offspring shown in bottom circles
48
What are characteristics controlled by
Single gene or several genes interacting
49
What are most characteristic controlled by
Multiple genes interacting
50
Alleles
Different versions of a gene that exist
51
How are alleles represented in genetic diagrams
A letter
52
How many alleles of each gene are there in the body
**2** - 1 in each chromosome in a pair
53
Homozygus
When organism has 2 alleles for particular gene that are the same
54
Heterozygus
When organism has 2 alleles for a particular gene which are different
55
Types of allele
- dominant
- recessive
56
Dominant allele
Allele in heterozygus gene that determines what characteristic is present
57
How are dominant alleles shown in genetic diagrams
Capital letter
58
Recessive allele
Other allele in homozygus gene that doesn't determine what characteristic is present
59
How are recessive alleles shown in genetic diagrams
Lower case letters
60
When does organism display recessive characteristic
When both alleles for particular gene are recessive
61
When does organism display dominant characteristic
When both alleles for particular gene are dominant OR 1 dominant allele + 1 recessive allele
62
Genotype
All genes + alleles an organism has
63
Phenotype
Characteristic determined by alleles, result of genotype
64
Carrier
Someone unaffected by an inherited disorder but can pass the allele on through reproduction
65
Inherited disorders
- cystic fibrosis
- polydactyly
66
What causes cystic fibrosis
Inheriting 2 recessive alleles
67
Cystic fibrosis
- genetic disorder of cell membranes
- body produces much thick sticky mucus in air passages + pancreas
68
How many people carry recessive cystic fibrosis allele
About 1 in 25
69
What causes cystic fibrosis carriers
Inheriting 1 recessive allele
70
What must parents be for child to have chance of having cystic fibrosis
Both have disorder OR are carriers
71
What causes polydactyly
Inheriting a dominant allele
72
Polydactyly
Genetic disorder where baby is born with extra fingers/toes
73
How are embryos screened for genetic disorders
- DNA taken from embryo and tested
- could then decide to terminate pregnancy
74
How are IVF embryos screened for genetic disorders
- before being implanted into womb:
- cell removed from each embryo - genes analysed
- embryos with bad alleles destroyed
75
Reasons for embryonic screening
- helps stop suffering
- treating disorders after birth expensive for government
- laws to stop it going too far - parents can't decide sex of baby (unless for health reasons)
76
Reasons against embryonic screening
- suggests people with genetic disorders 'undesirable' - could lead to prejudice
- more people may want embryo screened for desirable ones - e.g- blonde boy
- expensive
77
Types of variation
- genetic
- environmental
78
What causes genetic variation
Caused by differences in genotype
79
Environmental variation
Caused by interactions with condition phenotype lives in - e.g- plant grown on sunny windowsill grows luscious + green
80
What determines most variation
Mixture of genetic + environmental factors
81
Mutation
Rare, random change in organism's DNA that can be inherited
82
When do mutations occur
They are continuously occuring
83
What does mutation cause
Altered gene, producing genetic variant (different form of gene)
84
Effects of most mutations on phenotypes
no effect
85
Why do most mutations not affect phenotype
Most genetic variants have little/no effect on protein gene codes for
86
Example of variation having small influence on phenotype
- eye colour controlled by more than 1 gene
- mutation in 1 changes eye colour slightly
87
Example of variation having dramatic effect on phenotype
- gene coding for a protein that controls salt + water movement in/out of cells can become mutated
- leads to cystic fibrosis
88
What can cause rapid change in species
- environment changes
- new phenotype makes individual more suited to environment
89
Theory of Evolution
All of today's species have evolved from simple life forms that started developing over 3 billion years ago
90
Darwin's theory of evolution
Evolution by natural selection
91
Survival of the fittest
Organisms with most suitable characteristics for environment would be more successful competitors and more likely to survive
92
What happens to unsuccessful organisms in an environment
Death
93
What happens to successful organisms in an environmnt
Survival
94
What happens to surviving organisms in an envronment
Reproduction
95
What causes evolution
Beneficial characteristics become more common in genotype, species changes
96
Selective breeding
Humans artificially selecting plants/animals to breed so particular characteristics remain in population
97
What features are selectively bred
- useful
- attractive
98
Examples of selectively bred useful characteristics
- animals that produce more meat/milk
- crops with disease resistance
99
Examples of selectively bred attractive characteristics
- domestic dogs with gentle nature
- decorative plants with big/unusual flowers
100
Process of selective breeding
- select existing stock with desired trait
- breed them together
- select best offspring with desired trait
- breed them together
- continue process over several generations - desired trait will get stronger, then all offspring will have trait
101
Other name for selective breeding
Artificial selection
102
Problem with selective breeding
Reduces gene pool - number of different alleles in population as farmer selects similar plants/animals (inbreeding)
103
Problem with inbreeding
Higher chance of inheriting harmful genetic defects when gene pool limited
104
Problem with reduced gene pool
All closely related stock likely to be killed by new disease
105
What is genetic engineering
Process of transferring gene responsible for desirable from one organism's genome to another so it also has desired characteristic
106
Process of genetic engineering
- useful gene cut from organsism's genome using restriction enzyme
- insert gene into vector by ligase enzyme
- vector (usually plasmid/virus) with gene taken up by cell
- cell multiplied
107
Examples of genetic engineering
- bacteria modified to produce human insulin to treat diabetes - vector-plasmid
- crops have been modified to be resistant to disease or to produce bigger/better fruits
108
How to make organism develop with genetically engineered gene
Transfer gene in early stages of development - e.g- egg/embryo
109
Risks of genetic engineering
Changing organism's genome may accidentally create unplanned problems, passed on to future generation
110
Pros of genetically modified crops
- characteristic can increase yield
- crops could be engineered to contain missing nutrient in developing nations
- being grown in some places without problems
111
Genetically modified crops
Crops that have had genes modified
112
Cons of genetically modified crops
- may affect number of wild flowers, affecting number of insects - reducing farmland biodiversity
- may not fully understand effects of eating them on humans
- transplanted genes may get out into natural environment
113
Fossils
Remains of organisms from many thousands of years ago which are in rocks
114
What can fossils tell us
How much/little organsisms have evolved over time
115
Ways fossils form in rocks
- gradual replacement by minerals
- casts and impressions
- preservation
116
What kind of fossils form by gradual replacement by minerals
Things like teeth/bones don't decay easily, can last long time when buried
117
How does gradual replacement by minerals form fossils
- replaced by minerals as they decay
- forms rock-like substance shaped like original part
118
How do casts and impressions form fossils
- organism buried in soft material like clay
- clay hardens + organism decays, leaving cast of itself
**OR**
- footprints can be pressed into material when soft
- leaving impression when it hardens
119
How does preservation form fossils
- places where no decay happens
- because of problems with **decay microbes**
-glaciers - too cold to work
-peat bogs - too acidic
-tar pits - no oxygen/moisture so can't survive
120
Why can't scientists be certain about how life began on Earth
- many early life forms soft-bodied - left few traces behind
- few traces left behind mainly destroyed by geological activity
121
Why can bacteria evolve rapidly
They reproduce at a fast rate
122
How do bacteria become antibiotic resistant
- **mutations** of bacterial pathogens produce new strains
- causes **variation** - some strains are antibiotic resistant, some aren't
- those that aren't **die**
- those that are **survive**
- those that survive **reproduce**, passing on **gene** for antibiotic resistance
- bacteria have **evolved** to be antibiotic resistant
123
How to reduce rate of development of antibiotic resistant strains
- doctors shouldn't prescribe antibiotics inappropriately - for non-serious or viral infections
- patients should complete full course of antibiotics to kill all bacteria so none survive to mutate to be resistant
- restrict use of agricultural antibiotics - resistant bacteria can spread from animals to humans
124
Why is it difficult to keep up with new antibiotic resistant bacteria strains
Development of new antibiotics costly + slow
125
MRSA
- antibiotic resistant
- difficult to get rid of
- often affects people in hospital
- can be fatal if enters bloodstream
126
Classification
Organising living organisms into groups
127
Traditional classification system
Linnaean system (Carl Linnaeus)
128
Linnaeun classification system
- kingdom
- phylum
- class
- order
- family
- genus
- species
129
How did Linnaeus name organisms
- **binomial system**
- Genus
- species
130
Why classification systems changes over time
- improved knowledge of biochemical processes taking place inside organisms
- improved microscopes - improved knowledge of internal structures of organisms
131
Newer classification system
3 domain system (Carl Woese)
132
How are organisms grouped in 3 domain system
- split into 3 domains
- domains subdivided into kingdom, phylum, class, order, family, genus, species
133
3 domains
- archaea - primitive bacteria, usually living in extreme conditions
- bacteria - true bacteria
- eukaryota - broadly includes protists + fungi + plants + animals
134
What do evolutionary trees show
- **evolutionary relationships**
- how scientists think species are related to each other
- show common ancestors and relationships between species
135
How are evolutionary trees developed
- living organisms - current classification data
- extinct organisms - fossil data
136
Extinction
When there are no remaining individuals of a species still alive
137
Factors causing extinction
- **environment** changing too quickly
- new **predator** killing all
- new **disease** killing all
- can't compete with new species for **food**
- catastrophic **event**
