Variation & Selection Flashcards
1
Q
what does DNA stand for
A
DNA = Deoxyribonucleic Acid
2
Q
what is the monomer of DNA
A
DNA is a polymer
The monomer of DNA is nucleotides
3
Q
what structure does DNA have
A
DNA has the structure of a double helix (two strands coiled together)
4
Q
what is DNA
A
DNA is genetic material that is found is inside the nucleus, in chromosomes
5
Q
what are chromosomes
A
Chromosomes are DNA wrapped around a protein called histones
6
Q
where are genes located
A
Genes are located on chromosomes inside the nucleus
7
Q
what are genes
A
Genes = genetic material which codes for specific proteins
8
Q
how do genes control living organisms
A
By controlling which proteins our cells make, genes control living organisms’ features and characterisitics
9
Q
why are cells identical when mitosis
A
When cells divide, each cell is genetically identical
This is because DNA can replicate - when mitosis takes place, DNA is replicated
10
Q
what is a nucleotide made up of
A
Each nucleotide is made up of: deoxyribose (sugar molecule), phosphate molecule, a nitrogen-containing group called a base)
11
Q
what backbone does DNA have
A
DNA has a sugar phosphate backbone
12
Q
what are the 4 bases
A
ATCG (At Charlie’s Gateshead)
A = Adenine
T = Thymine
C = Cytosine
G = Guanine
13
Q
what bases are complimentary
A
AT are complimentary
CG are complimentary
14
Q
When do complemetary bases pair up
A
The complementary bases always pair up when the two strands of DNA come together - they cannot bind to other bases
This is called the base-pairing rule
15
Q
what bonds form between the bases
A
When they pair up, hydrogen bonds form between the bases
16
Q
which chemical can replicate itself in humans
A
DNA is the only chemical that can replicate itself identically
This means that it can be passed down through generations of cells as a genetic code
17
Q
what is the first step before mitosis
A
In cell division, the first step before mitosis is replication⟶ DNA makes copies of itself - so each daughter cell produced in mitosis is genetically identical
18
Q
how does DNA replicate (4)
A
The process of DNA replication:
1. Polynucleotide strands of DNA separate
2. Each original strand of DNA acts as a template strand
3. DNA polymerases use the base-pairing rule to assemble free nucleotides into two new strands of DNA
4. Two identical strands of DNA are formed - each new strand contains one original parent strand and a new complementary strand
19
Q
which DNA strand codes for protein
A
Only one of our strands of DNA codes for proteins
We call this the template strand
20
Q
what protein does the cell make the most
A
Most of the proteins that the cell makes are enzymes –> they control reactions within the cell
21
Q
what are some examples of structural proteins (3)
A
Examples of some structural proteins that are made are: keratin (in the skin) and myosin (in the muscles)
Some other proteins with important roles in the body are haemoglobin, and hormones
Proteins are chains of amino acids
22
Q
what is a triplet code
A
Triplet code = three bases that code for one amino acid
23
Q
what is a gene
A
A gene is a section of DNA for all the triplet codes for one protein
24
Q
how many natural amino acids are there
A
There are around 20 natural amino acids
25
what type of code is DNA how does it affect the proteins in other animals , think about other animals
and each of these amino acids have the same triplet code in almost all organisms
The DNA code is a universal code
26
where does protein synthesis happen
DNA stays in the nucleus but protein synthesis happens in the ribosomes which are in the cytoplasm
27
why cant dna be tranposrted as a whole
Our nuclear pores (holes in the nuclear membrane) are too small to transport our entire DNA out of the nucleus into cytoplasm
28
how is DNA transported
SO, for proteins to be made, the genetic code is first copied, and then transferred out of the nucleus, through the nuclear pores, into the cytoplasm
This is carried out by a DIFFERENT nucleic acid - RNA
29
what is rna
RNA = ribonucleic acid
30
differences between dna and rna (5)
Ribose and deoxyribose (the sugars) are very similar in structure
The bases Uracil and Thymine are also very similar in structure
The 3 main differences between DNA and RNA:
1. RNA contains the base Uracil (U) instead of Thymine (T)
2. DNA contains the sugar deoxyribose and RNA contains the sugar ribose
3. DNA is a double helix, RNA is just a single strand
31
what are the 2 types of RNA involved in protein syntehsis and what do they do (2)
2 Types of RNA involved in protein synthesis:
messenger RNA (mRNA) = makes a copy of the DNA code (think of it as a messenger between the nucleus and ribosomes)
transfer RNA (tRNA) = these TRANSFER amino acids from our cytoplasm to our ribosomes, to make the protein
32
what is another 3rd RNA
There is a 3rd RNA called ribosomal RNA (rRNA) = found in ribosomes - ribosomes are made of rRNA and protein
33
what are the stages in protein synthesis
The two stages of protein synthesis are:
1. transcription
2. translation
34
what is transcription
Transcription = when a copy of the genetic code for the protein is made and transported to the ribosome
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what is mRNA
mRNA = a copy of the genetic code
36
what is transcription flowchart (8)
Transcriptions:
1. Part of the DNA double helix unwinds
2. the DNA double helix unzips - the bonds between the bases are broken, allowing the two strands to separate from each other. This exposes the bases along the template strand
3. The template strand of DNA is used to form mRNA - RNA nucleotides are lined up along the template strand according to the base pairing rule
4. In the base pairing rule, Thymine is replaced with Uracil in RNA molecules
5. These RNA nucleotides line up in the correct order to form mRNA
6. The sugar-phosphate backbone is formed for the mRNA molecule by bonds forming between the ribose and phosphate groups
7. Once mRNA molecule is complete (when the entire section of DNA coding for the protein has been transcribed), it leaves the DNA, out of the nuclear pores, into the cytoplasm, to the ribosomes
8. DNA needs to zip up again
In transcription, our DNA triplet codes have been converted into RNA triplet codes
37
what is translation
Translation = converting the code in the mRNA into a protein
38
where does transcription happen
Transcription happens in the nucleus
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where does translation happen
Translation happens in the ribosomes.
40
what are 3 bases called
Codons = a triplet of bases
Each codon codes for: one amino acid
41
describe the flowchart for translation (7)
Translation:
1. mRNA arrives and attaches to the ribosomes
2. This stimulates the tRNA to begin their process
3. tRNA molecules attach to specific amino acids and bring them to the ribosome
4. When the tRNA arrives at the ribosome, the anticodon binds to the complementary codon on the mRNA
5. The first tRNA always binds to the start codon, which is AUG.
6. The first amino acid binds to the second, and when this bond forms, the first tRNA molecule is released to collect another amino acid
7. This process continues, until the stop codon is reached, which tells the machinery that the protein is complete, and it is released.
42
what are the 2 sites of tRNA for
Each tRNA molecule has 2 sites (like a pencil) - the pencil part has the anticodon
The other end of the tRNA molecule (eraser) is a site where a specific amino acid can attach (every amino acid has its own specific tRNA molecule)
43
what is an anticodon
Anticodon = a triple of bases which are complementary to the codon on mRNA
44
what is mutation
Mutation = a rare, random change in genetic material that can be inherited
45
when can mutation happen
A mutation can sometimes happen when DNA is replicating a mistake happens, like the wrong nucleotide being added to the sequence
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why is mutation bad
This leads to a gene mutation where the sequence of bases in a gene can change
This means that a different amino acid can become coded for
If even one amino acid changes, it can become an entirely different protein
47
what are the 4 types of mutation
dupliction
deletion
substitution
inversion
48
what is duplication in gene mutation
Duplication = nucleotide is inserted twice rather than once (duplicated) - the whole sequence from this point has been shifted up by one, so the whole gene is different and so will code for an entirely new protein
49
what is deletion in gene mutation
Deletion = a nucleotide is missed out - the whole sequence from this point has been shifted down by one, so the whole gene is different and so will code for an entirely new protein
50
what is substitution in gene mutation
Substitution = a different nucleotide is used -
51
what is inversion in gene mutation
Inversion = the sequence of the bases in the triplet is reversed. This does NOT have a knock on effect on the rest of the sequence. The effect of this mutation is the same as substitution, as only one triplet is affected
52
why does substitution differ from other mutations
this does not have a knock on effect on the sequence. This MIGHT mean that the triplet codes for a different amino acid. IF it does, this MIGHT mean, that it has a big effect on the protein. IF it does, this might change the function of the protein, or make it lose its function altogether.
53
with substitution, why might it not affect the amino acids
With substitution, it may not code for a different amino acid because most amino acids have more than one triplet that codes for them.
54
where can mutations happen
Mutations can happen in the body cells, or in the gamete/cells that divide to form gametes
55
what happens when the mutation affects body cells
If they happen in the body cells, it will mostly only affect those cells (liver, heart, skin)
56
what happens to mutated cells
This mutated cell will either die if harmful, (the mutation dying with it), or if the mutation does not majorly affect the functioning of the cell, so it will become a group of mutated cells (which will die with the organism)
57
what happens to mutated gametes
HOWEVER if the mutation happens in a gamete/cells that divide to form gametes, then it can be passed down to the next generation (these are genetic diseases)
58
what processes used genetic mutations to their advantage
Genetic mutations can give an advantage - a process that uses this is natural selection
59
what is natural selection
A genetic mutation can lead to an individual being better adapted to their environment
As they are better adapted to their environment, they are more likely to survive
As they are more likely to survive, they are more likely pass on this advantageous allele on to future generations
This is natural selection
60
how do insects become resistant aswell as bacteria to anitbiotics
This is how insects can become resistant to insecticides and how bacteria develop resistance to antibiotics, through natural selection
61
do mutations occur randomly
Gene mutations occur randomly in all organisms
62
what are mutagens
Substances that increase the rate at which mutations occur
63
what are some mutagens
1. Ionising radiation - UV, X-rays, Gamma Rays
2. Chemicals in cigarette smokes
3. Chemicals like mustard gas and nitrous oxide
64
how many DNA molecules does a chromosome contain
Each chromosome contains one DNA molecule
65
what is DNA coiled around to form what
DNA is coiled around a protein called histone to form chromosomes
66
why do genees differ in a chromosome as you go from one chromosome to the next
As each chromosome only contains one DNA molecule, each chromosome contains a very specific set of genes - the genes in a chromosome differ as you go from one to the next
67
do all organisms have 46 chromosomes as humans
Different organisms have different numbers of chromosomes
68
what are homologous pairs and how many in humans
Chromosomes are in homologous pairs (matching pairs)
Humans have 22 pairs of homologous chromosomes, however the last pair is different ⟶ these are our sex chromosomes
The sex chromosomes consist of X and (maybe)Y chromosome
69
why do we have pairs of chromosomes
The reason why we have PAIRS of chromosomes is because we get ONE from EACH parent
This is why for the sex chromosomes we have two - one from mum, one from dad
Females always have XX
Males have XY
70
what are haploid and dipload cells
We can have haploid and diploid cells
HA for HALF - haploid cells have HALF the number of chromosomes - these are our gametes
Gametes = sex cells (egg cell/ovum and sperm cell)
Diploid cells = Di = 2 = we have DOUBLE the number/all of our chromosomes - we have all the PAIRS
71
what is the only cell in the body that has no chromosome
the only cell in the body that has no chromosomes because it has no nucleus are our red blood cells
72
what process are gametes formed via? and why
Gametes are formed via meiosis
Meiosis produces haploid cells in order to restore the complete/full number of chromosomes upon fertilisation
Fusion of the nuclei of the gametes to form a diploid zygote
73
what is a genome
genome = all the genes in the genetic makeup/DNA of an organism
74
how much of our DNA codes for proteins
Only around 1.5% of our DNA is made up of genes that code for proteins
75
what are alleles
Alleles = different forms of the same gene
76
how do proteins contribute to our features
The proteins that genes code for contribute to particular features in the body
This feature can vary from eye colour to blood type (what type of antigen is present on the surface of red blood cells)
77
are homologous pairs identical genetically
In a homologous pair of chromosomes, it’s not that the two chromosomes in the pair are genetically identical
With homologous pairs of chromosomes, they carry DIFFERENT alleles in each chromosome, for the SAME features
78
what is a location of a gene in a chromosome called
The location of a gene on a chromosome = loci (pronounced low kai)
79
what is a dominant allele
Alleles can be dominant or recessive
Dominant allele = it will be expressed in the phenotype
80
what is a recessive allele
Recessive allele = will only be expressed in the phenotype in the absence of a dominant allele
81
what are genes called that code for proteins
Genes that code for proteins are called structural genes
82
what are operons
Operon = a group of structural genes that is linked to an operator and promotor
83
what are operons under the control of
Operons are under the control of regulatory genes
84
what is and does the promoter do
The promoter starts transcription by binding to an enzyme called RNA polymerase
85
what is a regulatory gene
The regulatory gene codes for a protein called a repressor
86
what is a repressor and what does it do
The repressor binds to the operator, and they stop the promotor from binding to the RNA polymerase, thus stopping transcription
87
why is there variation in sexual then asaxual (2)
1. With sexual reproduction, there is huge variation in the gametes
2. Fertilisation occurs very randomly - one egg cell out of many released, and one sperm cell out of thousands that compete, fuse
88
how do identical twins come about
Identical twins come from the same zygote (they can also be called monozygotic twins)
When the zygote undergoes its first mitosis, the first two cells do not form together, but separate and act as separate zygotes, undergoing mitosis to form two foetuses
As they have originated from the same zygote, they are genetically identical (as mitosis produces genetically identical/clones cells)
89
how do non indentical twins come about
Non-identical twins form from two different zygotes that are not genetically identical, so there will be 2 eggs available instead of 1, and each will be fertilised by different sperms
90
how are seeds made in plants (3)
Seeds are made by sexual reproduction in plants
The embryo in the seeds are made by the pollen grain nucleus fusing with the egg cell nucleus
Embryos from the same plant will have variation as you have different pollen grains fertilising different egg cells so you have different combinations of genes
91
what is cloning
Cloning = a process that produces a group of genetically identical offspring
92
variation is determined by?
Variation is determined by genes, but the environment as well
93
When considering environmental effects for growth on plants, what should u think abt
When considering environmental effects for growth on plants, think about the factors that affect rate of photosynthesis
94
how do genotypes and phenotypes work (3)
1. Each feature in a phenotype is controlled by a gene
2. There are two alleles for each gene, one found on each chromosome given by each parent
3. One allele can be dominant over the other, recessive allele
95
what is a dominant allele
A dominant allele = one that will be expressed in the phenotype
96
what is a receccive allele
A recessive allele = one that will only be expressed in the phenotype in the absence of a dominant allele
97
whats the difference between homozygous and heterozygous
Homozygous pair = (homo = same) = both alleles are dominant/both alleles are recessive
Heterozygous pair = (hetero=different) = a pair with two different alleles - one dominant and one recessive
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