Inheritance, variation and evolution (need to add from variation onwards) Flashcards
1
Q
What are chromosomes?
A
long strands of DNA usually found in pairs
2
Q
What is DNA?
A
a chemical that all the genetic material of a cell is made up from which contains coded material that determines characteristics
3
Q
What is a gene?
A
a small section of DNA found on a chromosome which codes for a particular sequence of amino acids which make a specific protein
4
Q
What is a genome?
A
the entire set of genetic material in an organism
5
Q
Why is understanding the genome important for science and medicine?
A
- it allows scientists to identify genes linked to different diseases which helps to develop effective treatments for them
- genomes can help to trace migration patterns of populations to help work out when new populations split off and what route they took
6
Q
What are nucleotides?
A
repeating units which make up DNA strands (making the strands polymers)
7
Q
What does one nucleotide consist of?
A
- one sugar molecule
- one phosphate
- one base
8
Q
What is a backbone formed from (in a nucleotide)?
A
one sugar and one base
9
Q
What is complementary base pairing?
A
the idea that base A always pairs up with base T and base C always pairs up with base G
10
Q
Which bases always pair together?
A
A and T
C and G
11
Q
What does the order of bases in a gene determine?
A
the order of amino acids in a protein
12
Q
What is mRNA and what does it do?
A
it is a molecule which carries a code from the DNA to the ribosome so that proteins can be made in the cytoplasm by the ribosomes
13
Q
Give some examples of proteins
A
- enzymes (biological catalysts)
- hormones (carry messages around body)
- structural proteins (physically strong)
14
Q
What are mutations?
A
random changes to DNA
15
Q
How do mutations occur?
A
continuously and randomly
16
Q
Do mutations have much affect?
A
they mostly have no effect because they code for the same amino acid so that its function/appearance is unaffected
sometimes they alter the amino acid and therefore the protein so that its shape/function is affected
17
Q
What are the three types of mutations?
A
insertion (adding an extra base)
deletions (loosing a base)
substitution (replacing a base)
18
Q
What is an insertion mutation?
A
where a new base is inserted into the DNA base sequence where it shouldn’t be
19
Q
What is a deletions mutation?
A
when a random base is deleted from the DNA base sequence
20
Q
What is a substitution mutation?
A
when a random base in the DNA base sequence changes to a different base
21
Q
What are the two types of reproduction?
A
sexual
asexual
22
Q
What is sexual reproduction?
A
where genetic information from two organisms (father and mother) is combined to produce offspring which are genetically different to both parents (which has half of its chromosomes from each parent -23 each)
23
Q
What is asexual reproduction?
A
reproduction by only one parent which produces a genetically identical offspring (a clone)
24
Q
What is fertilisation?
A
the fusing of gametes (eg. egg and sperm) in sexual reproduction to form a cell (fertilised egg) with the full number of chromosomes
25
What are gametes?
sex cells with half the number of chromosomes as a normal cell
eg. egg and sperm
26
What is meiosis?
cell division which produces cells with half of the number of normal chromosomes (gametes)
27
Describe the process of meiosis
- the cell's genetic information duplicates
- in the first division, the chromosome pairs line up in the centre of the cell and the nucleus and cell splits (with half of the chromosomes in each)
- in the second division, the chromosomes line up in the centre of the cell and the arms of the chromosomes get pulled apart
- you get four gametes, each with a single set of chromosomes which are all genetically different to each other
28
What is the cell cycle?
the cycle where body cells in multicellular organisms divide to produce genetically identical cells
29
Why does the cell cycle take place?
to grow new cells or replace damaged cells
30
What are the two stages of the cell cycle?
- growth and DNA replication
| - mitosis
31
Describe what happens in the growth and DNA replication stage of the cell cycle
- the DNA spreads out into long strips
- the cell grows in size
- the number of subcellular structures (eg. mitochondria and ribosomes) increase
- the DNA then duplicates so that there's one copy of reach new cell
32
Describe what happens in mitosis in the cell cycle
- the chromosomes line up at the centre of the cell and cell fibres pull them apart
- the nucleus divides (membranes form around each of the sets of chromosomes, which becomes the nuclei of the two new cells)
- the cytoplasm and cell membrane divide
- two genetically identical daughter cells have been produced
33
What are the advantages of sexual reproduction (compared to asexual)?
- offspring have different genes so that there is variation
- variation increases chance of species surviving a change in environment
- better adaptions will give a better chance of survival so that they are likely to breed and pass on desired characteristics (natural selection)
- can use selective breeding
34
What are the advantages of asexual reproduction (compared to sexual)?
- only one parent is needed
- uses less energy because organisms don't need to find a mate
- faster
- lots of identical offspring can be reproduced
35
What chromosomes determine your gender?
X and Y chromosomes
XY - male (Y codes for male)
XX - female
36
What is a phenotype?
a physical characteristic (you can see)
37
What is a genotype?
the different genes that gives someone a physical characteristic
38
What is a dominant allele?
an allele where you only need to inherit one to have that characteristic
39
What is a recessive allele?
an allele where you have to inherit two to have that characteristic
40
What is a homozygous trait?
where an organism has two alleles for a particular gene which are the same
41
What is a heterozygous trait?
where an organism has two alleles for a particular gene which are different
42
What is cystic fibrosis?
an inherited disorder of cell membranes caused by a recessive allele
it causes the body to produce a lot of thick mucus in air passages and the pancreas
43
What is polydactyly?
an inherited disorder caused by a dominant allele which causes people to have extra fingers or toes
44
What is embryo screening?
a way to see if embryos have genetic disorders by removing a cell from an embryo (in the womb or from IVF) and studying its DNA
45
What are the advantages of embryo screening?
- can stop people suffering
| - there are laws to stop it going too far
46
What are the disadvantages of embryo screening?
- unethical (IVF embryos will be destroyed and women may choose to have an abortion)
- creates prejudice against people with genetic problems
- expensive
- there may become a point where everyone wants to screen their embryo to get a "desirable" child
47
Give some examples of inherited disorders
polydactyly
| cystic fibrosis
48
What experiment did Mendel do? And what did this reveal?
he bred pea plants (with different heights)
| he found that when he bread a tall and short plant together, the offspring were tall, showing that tall was dominant
49
What conclusions did Mendel reach?
- characteristics in plants are determined by hereditary units
- hereditary units are passed onto the offspring unchanged from both parents (one from each parent)
- hereditary units can be dominant or recessive
50
What is variation?
differences within a species
51
What are the two types of variation?
genetic variation
| environmental variation
52
What is genetic variation?
variation caused by different genes because all organisms inherit characteristics from their parents
53
What is environmental variation?
variation due to different environments (conditions where an organisms lives and grows) affecting individuals in a species
54
Give some examples of variation caused by genetics
eye colour
| blood group
55
Give some examples of variation caused by environment
scars
56
Give some examples of variation caused by genetics and environment
weight
height
skin colour
57
What does the theory of evolution state?
all of today's species have evolved from simple life forms that started to develop over three billion years ago
58
Who came up with evolution?
Charles Darwin
59
What is the survival of the fittest?
the idea that organisms with the most suitable characteristics for its environment will be most successful so are more likely to survive and pass on their genes, whereas the less well suited organisms will not survive.
60
What is speciation?
the idea that over a long period of time, the phenotype of an organism can change so much so that a new species will form
61
What is extinction?
when a species completely dies out
| eg. the dodo
62
What can cause a species to become extinct?
- environment changes too quickly (eg destruction of habitat)
- predators
- a new disease
- can't compete with another species for food
- catastrophic event (eg volcanic eruption)
63
Why did it take a long time for anyone to except Darwin's theory of evolution?
- it goes against religion
| - when he came up with his theory, there wasn't enough explanation or evidence (genes hadn't been discovered)
64
What was Lamarck's theory?
useful changes of an organism acquires during its lifetime will be passed on to its offspring
65
What is selective breeding?
when humans artificially select animals or plants that are going to breed so that particular genes remain in a species.
66
Why are some organisms selectively bred?
- to produce more meat/milk
- to have a gentler nature
- to have a more appealing appearance
- to be disease resistant
67
Explain the process of selective breeding
- the most suited animals are selected and bred together
- the most suited male and female offspring produced are bred together
- the process continues until all the animals have the desired trait
68
What is the main disadvantage of selective breeding?
it can result in inbreeding and the animals may all be too similar (because of the reduced gene pool -number of genes in a species)
- this can cause genetic defects and health problems
- this can mean the entire species can be easily wiped out by a disease because of the lack of variation
69
What is genetic engineering?
Where a gene responsible for a desired characteristic is transferred from one organism's genome to another's, so that it too has that desired characteristic
70
Explain the process of genetic engineering.
- a useful gene is isolated (cut) from one organism's genome using enzymes and is inserted into a vector (the vector is usually a virus or bacterial plasmid)
- the vector is introduced to the target organism and the useful gene is inserted into its cells
71
Give some examples of what genetic engineering could be used for
- bacteria have been engineered to produce human insulin to help treat diabetes
- crops are modified to make them resistant to disease and insects and to improve the quality of their produce
72
What are the advantages of genetic engineering?
- more food can be produced from an increased yield of crops
| - crops can be modified to include nutrients that some populations are lacking
73
What are the disadvantages of genetic engineering?
- using GM crops could reduce biodiversity because the number of wild flowers or insects could be affected
- some people are still uncertain about the safety of eating modified crops because they may affect human health
- transplanted genes may get out into the natural environment
74
What methods are their for cloning plants?
tissue culture
| cuttings
75
How are plants are cloned using tissue culture?
a few plant cells are put in a growth medium with hormones and they grow into new plants
76
What are the advantages of cloning plants using tissue culture?
- can grow very quickly
- can grow in very little space
- can be grown all year round
- helps preserve rare plants
- produces lots of stock for plant nurseries quickly
77
How are plants cloned from cuttings?
gardeners take cuttings from good parent plants and then plant them, so that they grow to produces clones
78
What are clones?
genetically identical copies
79
What are the advantages of cloning plants from cuttings?
- can be produced quickly
- cheap
- simpler than cloning from tissue culture
80
How can animals be cloned?
embryo transplants
| adult cell cloning
81
How can animal clones be made using embryo transplants?
- sperm cells are taken fro a prize bull and egg cells are taken from a prize cow
- this sperm artificially fertilises the egg
- the embryo which develops is then split multiple times before the cells become specialised to give lots of cloned embryos
- these embryos are then implanted into lots of cow's wombs and grow into genetically identical calves
82
How can animals be clone using adult cell cloning?
- a unfertilised egg cell is taken and its nucleus is removed
- a nucleus is taken from an adult body cell and is inserted into the empty egg cell
- this is given an electric shock
- once the embryo has grown slightly, it is inserted into the womb of a cow and is grown to make a calve genetically identical to the adult whose nucleus was used
83
What are the advantages of cloning animals?
- get a lot of ideal offspring
- could lead to a better understanding of embryo development, aging and age related disorders
- helps preserve endangered species
84
What are the disadvantages of cloning animals?
- could get a reduced gene pool (fewer different alleles in a population) meaning the species could easily be wiped our by a new disease
- cloned animals may not be as healthy as others
- worry that humans might be cloned in the future
85
What are fossils?
remains of organisms from thousands of years ago, which are found in rocks
86
What are the three ways fossils could be formed?
- from gradual replacement from minerals
- from casts and impressions
- from preservation in areas where no decay can happen
87
How can fossils be formed from gradual replacement from minerals?
things like bones, teeth and shells decay very slowly so last a long time when buried
they're eventually replaced by minerals as they decay, which forms a rock-like substance that is the same shape as the original bones
the surrounding sediments can turn into rock but the fossil stay distinct inside it
88
How can fossils be formed from casts?
when an organism is buried in a soft material (like clay) , the soft material hardens around it
the organism then decays, which leaves a cast of itself
89
How can fossils be formed from impressions?
an object (eg footprint) can be pressed into soft materials, which leaves an impression as it hardens
90
How can fossils be formed from preservation in places where no decay happens?
in amber and tar pits, there's no oxygen and moisture so decay microbes can't survive
in glaciers, it's too cold for decay microbes to work
in peat bogs, it's too acidic for decay microbes
