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B6 Flashcards

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1
Q

what happens during sexual reproduction?

A

2 parents
genetic info is mixed leading to variation in offspring
sperm/pollen and egg cells fuse
involves meiosis

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2
Q

what happens during asexual reproduction?

A

1 parent
no mixing of genetic info or fusion of gametes
no variation leads to identical offspring/clones
only involves mitosis

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3
Q

Define DNA

A

Deoxyribonucleic avid
Chemical
All genetic material is made up of it
Contains coded info

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4
Q

DNA structure

A

Polymer
2 strands coiled
Double helix
Repeating units called nucleotides*

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5
Q

Define chromasomes

A

Long molecules of dna

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6
Q

Define genes

A

Small sections of DNA

Code for specific AAs for specific proteins

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7
Q

How many AA’s are used

A

20

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8
Q

What does DNA determine

A

Which proteins are produced by a cell

And what type of cell it is

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9
Q

Define genome

A

Entire set of Genetic info in an organism

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10
Q

Why is understanding the genome important?

A

Scientists can :
Identify genes linked to types of diseases
Which can help create effective treatments
Trace migrations of populations and what route new populations took

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11
Q

What’s a nucleotide?

A

Repeating unit

Consists of 1 sugar molecule, 1 phosphate molecule and 1 base

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12
Q

Bases in DNA

A

AT
CG
(Complimentary vase pairing)

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13
Q

What decides the order of AA’s in a protein?

A

The order of bases

Each AA is coded for by a sequence of 3 bases in the gene

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14
Q

What are non-coding parts of DNA?

A

Don’t code for proteins
Some switch on and off
This controls whether a gene is expressed or not
(Used to make proteins)

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15
Q

Role of mRNA

A

Carries code template from nucleus to ribosome

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16
Q

How are correct AAs brought to ribosomes

A

By carrier molecules

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17
Q

Functions of proteins

A

Enzymes -> speed up chemical reactions in body
Hormones-> carry messages around body
Structural proteins -> physically strong

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18
Q

Define mutations

A

Random change in genetic code
Can be inherited
Continuous and can be spontaneous

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19
Q

What do mutations do to genes?

A

Change sequence of DNA bases
Produces genetic variant
The sequence codes for AAs to make proteins so the protein made can change

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20
Q

What increases chance of mutation?

A

Exposure to certain substances or radiation

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21
Q

How do mutations effect proteins ?

A

Most mutations have little/no effect
Some change it to a small extent so it’s function /appearance isn’t affected
-some mutations are serious and will code for an altered protein with a diff. shape that can affect its function

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22
Q

What happens when enzymes or structural proteins change their shape due to mutations

A

Enzyme - active site changed so substrate can’t bind

Structural- lose strength and can’t provide structure/support (collagen)

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23
Q

What happened when there’s a mutation in non-coding DNA

A

The way genes are expressed can change

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24
Q

Explain insertion mutations

A

New base inserted into DNA sequence where it shouldn’t be
Changes how 3 bases are read so AA coded for can change
More than one AA can be affected due to knock on effect

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25
Codon/triplets
3 bases for coding
26
Describe deletion mutations
Random base deleted from DNA base sequence Change how bass sequence is read Knock on effects to rest of sequence
27
Describe substitution mutation
Random base in DNA sequence is changed to a different base
28
Describe sexual reproduction
Genetic info from 2 organisms (mother+father) to produce genetically diff. Offspring from the parents
29
How does sexual reproduction occur
By meiosis gametes fuse and genetic info is mixed Fertilisation That’s why offspring inherits features from both parents due to getting a mixture of chromosomes
30
How do offspring get the full amount of chromosomes
Get half from each parent
31
Describe asexual reproduction
Only one parent Genetically identical Mitosis No fusion of gametes
32
How are gametes made
By meiosis
33
What happens to the cell after meiosis
Divides by mitosis to make a copy of itself Repeats this many times to make lots of new cells in an embryo As embryo develops the cells differentiate into different types of specialised cells to make up the whole organism
34
Add of sexual reproduction
Mixing genetic info increases variation so change of survival in a change of environment increases So they’re more likely to breed successfully and pass on genes by natural selection
35
How can natural selection be sped up
By selective breeding
36
What’s selective breeding?
Breeding animals with desired characteristics to produce offspring with those characteristics
37
Adv. if asexual reproduction
1 parent -> less energy, don’t need to find a mate Faster Identical offspring can be produced in favourable conditions
38
How do malarial parasites reproduce asexually
infected mosquito bites human it injects plasmodium that affects our tissue. Each parasite replicates asexually and invade RBC and multiply to cause symptoms
39
How do malarial reproduce sexually
inside mosquito | by meiosis
40
How do fungi reproduce asexually
By mitosis | Asexually produces spores are genetically identical to parent fungus
41
How do fungi reproduce sexually
2 hyphae from diff. fungi join by meiosis to make haploid spores Happens in favourable conditions
42
Explain what it means that fungi are heterotrophic
Can’t do photosynthesis as they use organic compounds as sources of energy
43
How do plants reproduce asexually
Runners (stems) that grow to the surface of soil horizontally away from plant , along it new identical plants form Bulbs -> new bulbs divide off from main bulb and grow into new identical plants
44
How many pairs of chromosomes just control characteristics?
22 pairs
45
Which pair determines sex? | Male + Female
23rd pair Male - XY Female - XX 50% chance for each gender
46
What are most characteristics controlled by?
By several genes interacting
47
Define allele
Diff versions of a gene
48
Define genotype
The combination of alleles you have
49
Define phenotype
The characteristics you have | Expresses alleles
50
How can embryos be screened for genetic disorders during IVF
Before being implanted into Mother’s womb a cell can be removed to analyse its genes Or dna can be taken from an embryo in the womb
51
Against embryonic screening
Implies ppl with genetic problems are undesirable -> increases prejudice Can be used to pick designer babies Can be expensive Embryos with “bad” alleles are destroyed
52
For embryonic screening
Stops ppl suffering Treating disorders costs tax payers/govt a lot of money There are laws to stop it going too far (atm you can’t chose the gender unless it’s for health reasons)
53
Describe Mendel’s experiment
1) took a tall + draw pea plant and cross breeded All offspring were tall pea plants 2) took 2 of the tall pea plant offspring and cross breeded 3 tall + 1 dwarf offspring
54
What did Mendel’s experiment show?
Height characteristics in pea plants was determined by separately inherited “hereditary units” passed on from each parent Ratio of tall + dwarf offspring show the unit for tall “T” was dominant over the dwarf “t” and it was recessive
55
Mendel’s 3 conclusions
Characteristics in plants are inherited by hereditary units Hereditary units are passed on to offspring unchanged (one unit from each parent) A unit can be dominant or recessive but the dominant characteristics will be expressed
56
Why was Mendel not believed initially?
There was no background knowledge/understanding or ideas about genes, DNA and chromosomes Couldn’t explain why characteristics were inherited
57
*check end of pg.94*
*
58
Define environmental variation
When the environment/conditions organisms lives/grow in causes differences between members of the same species
59
What are most characteristics due to?
Genes AND the environment
60
What do mutations introduce?
Variation | Phenotype can be fully or slightly changed
61
Define theory of evolution
All of today’s species have evolved from simple life forms that started to develop over 3 billion years ago Darwin
62
Evidence for theory of evolution
Fossils
63
Explain survival of the fittest
Organisms with more suitable characteristics for the environment are more successful competitors and would be more likely to survive and reproduce and pass on beneficial genes/characteristics
64
Why was Darwin’s theory not initially accepted?
Couldn’t explain why new characteristics appeared or why beneficial adaptations were passed onto offspring Religion Not enough evidence
65
Why was Darwin’s theory eventually accepted?
Discovery of genes/genetics with the microscope | Phenotype
66
What’s speciation?
Development of a new species | Populations of the same species change and become reproductively isolated
67
Define extinction
No individuals of a species remain
68
Reasons for extinction
- environment chanted to quickly - new predator kills them all - new disease kills them all - can’t compete with a new species for food - catastrophic event kills all (eruption)
69
Explain Lamarck’s theory
If a characteristic was used a lot by an organism it would become more developed during its lifetime and its offspring would inherit the acquired characteristic
70
How do you find out if a hypothesis is correct ?
Try and find evidence | Or try and disprove it
71
Why was Lamarck’s theory rejected ?
Experiments didn’t support his hypothesis | Discovery of genetics supported Darwin’s idea as it explained how characteristics are passed on (resistant bacteria)
72
Who’s idea was natural selection ?
Wallis
73
Define natural selection
Same as survival of the fittest
74
What’s selective breeding
Humans artificially select plants/animals to breed so desires genes remain in the population
75
Selective breeding features
More meat/milk (yield) Disease/pest resistant crops Gentle temperate/well behaved animals Decorative plants with big/unusual flowers
76
Process of selective breeding
Choose existing stock with desired characteristics breed them together select best offspring and breed them continue over generations as desired trait gets stronger until all offspring have it
77
Drawbacks of selective breeding
Less variation Reduces gene pool -> less chance of resistant alleles being present Inbreeding -> genetic disorders/mutations
78
Define genetic engineering
Transfer of a gene responsible for a desirable characteristic from one organism to another
79
Genetic engineering process
1) useful gene isolated / cut from one organism’s genome with restriction enzymes 2) insert into vector 3) vector is usually a virus or bacterial plasmid 4) when the vector is introduced to the target organism the useful gene is inserted into its cells 5) stick with ligase
80
Uses of GM
Bacteria -> produce human insulin to treat diabetes | GM Crops-> disease/pest/herbicide resistance
81
cons of GM crops
Reduce biodiversity Eating them could affect human health Transplanted genes could get into the natural environment (interbreed)
82
Pros of GM crops
Increase yield -> more food Can provide nutrients in developing countries Already grow in other places with no issues

Biology (7 decks)

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