Exam Revision Flashcards
1
Q
what does dna stand for?
A
deoxyribonucleic acid
2
Q
how many cells in a multicellular organism possess the full set of dna required for that organism?
A
all of them
3
Q
what does dna do?
A
- determines characteristics
- gives instructions to cells to make proteins
4
Q
who first described the structure of dna and when?
A
james watson and francis crick in 1953
5
Q
what shape is dna?
A
a twsited double helix
6
Q
how does the structure of dna change in different organisms?
A
it stays the same
7
Q
what is dna made up of?
A
smaller molecules called nucleotides
8
Q
what is a nucleotide made up of?
A
phophate group, deoxyribose sugar, nitrogen-rich base
9
Q
what makes up the sides of dna strands?
A
deoxyribose sugar and phosphate groups
10
Q
which part of the side of dna strands are the bases connected to?
A
the deoxyribose sugara
11
Q
what are the 4 nitrogen-rich bases?
A
adenine, thymine, guanine, cytosine
12
Q
which bases pair together?
A
adenine pairs with thymine, guanine pairs with cytosine
13
Q
what is the base pairing known as?
A
complementary base pairing
14
Q
what is the percentage of adenine in a dna strand equal to?
A
the percentage of thymine
15
Q
what is the percentage of guanine in a dna strand equal to?
A
the percentage of cytosine
16
Q
what are chromosomes?
A
long thread-like structures found in the nuclei of all cells in the human body that contain a nucleus
17
Q
what are chromosomes made up of?
A
each chromosome is one very long dna molecule wrapped around proteins
18
Q
how many chromosomes does each cell have?
A
46
19
Q
how much dna makes up all 46 chromosomes?
A
2 metres worth
20
Q
what are sperm and egg cells called?
A
gametes
21
Q
do sperm and egg cells have 46 chromosomes?
A
no, they have 23 each
22
Q
what determines the sex of a baby?
A
the sperm
23
Q
how many sex chromosomes are there per cell?
A
2
24
Q
what are the 2 sex chromosomes?
A
x and y chromosomes
25
which sex chromosomes are found in a female?
2 x chromosomes
26
which sex chromosomes are found in a male?
1 x chromosome and 1 y chromosome
27
what are the other 44 chromosomes (not sex chromosomes) called?
autosomes
28
how are autosomes grouped?
into 22 pairs
29
what characteristic does each pair of autosomes have?
they are homologous (meaning the same)
30
what are the features of a homologous pair?
- each chromosome is the same length
- each chromosome has a structure called a centromere in the same position
- each chromosome has genes for particular characteristics at the same location along their length
31
what is a karyotype?
an organism's complete set of chromosomes
32
what is the human karyotype?
46 (ordered in length from shortest to longest)
33
what are genes?
sections of dna arranged along a chromosome that code for specific proteins
34
how many genes are on each chromosome?
200-2000
35
what are the differences between genes?
- the order of bases along the dna strand is different
- the number of bases in that section of dna is different
36
what are proteins?
they create the structures and perform actions needed for cells to survive, grow, and function
37
what are the 3 types of proteins?
structural proteins, enzymes, and regulatory proteins
38
what are examples of structural proteins?
- collagen (found in tendons and ligaments)
- keratin (found in skin, hair, nails, scales, feathers)
39
what are examples of enzymes?
- amylase (helps digest starch)
- lactase (helps digest lactose)
- lipase (helps digest fats)
40
what are examples of regulatory proteins?
- growth hormone (stimulates growth and cell reproduction)
- insulin (controls blood glucose levels)
41
do the proteins coded by genes have the same outcome in every organism?
no, keratin can create hair in dogs but scales on snakes, they can be different
42
what is formed when an egg and sperm cell join?
a zygote
43
how many chromosomes does a zygote have?
46
44
what is a zygote?
a single cell
45
how do zygotes replicate?
through mitosis
46
why does the body never stop replicating cells, even when fully developed?
in order to replace damaged or dead cells
47
what is mitosis?
a process of cell division where 2 identical daughter cells are produced from a single parent cell
48
how much time doe a cell spend in mitosis?
10% of the time
49
what has to occur before mitosis?
interphase
50
what is interphase?
dna replication + growth
51
how does dna replicate during interphase?
1. complementary strands break apart, leaving exposed/unpaired bases
2. nucleotides begin to attach to exposed bases (in complementary base pairs)
3. 2 identical strands of dna are formed
52
what can occur if mitosis is too uncontrolled and rapid?
cancer and other genetic mutations
53
what are the steps of mitosis?
1. prophase (chromosomes condense)
2. prometaphase (chromosomes continue to condense)
3. metaphase (chromosomes are lined up at the equator of the cell)
4. anaphase (sister chromatids separate and are now called chromosomes, tey are pulled towards opposite poles of the cell)
5. telophase (chromosomes arrive at opposite poles and begin to decondense)
6. cytokinesis (cell membrane separates parent cell into 2 daughter cells)
54
what is translation?
when the information in dna is used to produce a protein
55
do chromosomes ever leave the nucleus of a cell?
no
56
what is it called when a copy of dna is made?
transcription
57
what happens to the transcripted dna?
it moves to the ribosomes where proteins are made (translation)
58
how do ribosomes read dna?
in groups of 3 called triplets/codons
59
what does each triplet of dna do?
gives instructions for what amino acids need to be added to the protein
60
do different species have different amino acids?
no, dna is universal
61
what are genetic mutations?
changes to a dna sequence that occur during cell division
62
what do mutations do?
they change the information that your cells need to form and function
63
what is a negative of gene mutations?
they can lead to genetic conditions such as cancer
64
what is a positive of gene mutations?
they can help humans better adapt to their environments
65
what are possible symptoms of gene mutations?
- physical characteristics (e.g. facial abnormalities, cleft palate, etc.)
- problems with cognitive/intellectual function
- developmental delays
- vision or hearing loss
- breathing problems
- increased risk of developing cancer
66
when do genetic mutations occur?
during cell division
67
what are the types of mutations?
silent, frameshift, nonsense, and missense
68
what is a silent mutation?
a mutation that doesnt affect the individual (a single base on the dna strand is changed that does not affect the protein that is coded by that gene)
69
what is a missense mutatiom?
a mutation that doesn't stop the gene from creating a protein, but the protein produced is a different one (protein may not function properly and cause disease)
70
what is a nonsense mutation?
a mutation that causes cells to stop reading the information on the gene before the protein is fully coded, because a stop codon was coded too early (protein created is incomplete and cannot function at all)
71
what is a frameshift mutation?
a mutation that involves the insertion or deletion of one or more bases, which jumbles all the bases after the mutation (can still read for a protein, however it can be the wrong protein, can be nonsense or missense)
72
what is a point mutation?
a mutation where only one base is replaced with another (can be silent, can code for a different protein, can create a nonsense mutation)
73
what are agents that cause mutations known as?
mutagens
74
what are agents that cause mutations that lead to cancer known as?
carcinogens
75
what are examples of mutagens?
uv light, cigarette smoke, asbestos, mustard gas, benzene
76
what is a positive of genetic modification at the embryotic stage?
it can make people resistant to hereditary disease/conditions and remove harmful mutated genes from the gene pool
77
what is a negative of genetic modification at the embryotic stage?
its morally unethical, as people may take advantage of the technology and completely alter their child's dna, resulting in a reduction of human diversity and an increase in social inequality
78
what is the technology that is used for genetic modification called?
crispr cas9
79
how does crispr cas9 work?
it works on the principle that any section of a person's dna can be cut out as long as it is replaced with different dna
