1
Q
what is heredity
A
how traits are passed down
2
Q
what are traits
A
things that are encoded within DNA
3
Q
what are the nitrogenous bases in DNA
A
adenine, thymine, cutosine, guanine
4
Q
what are the nitrogenous bases in RNA
A
adenine, uracil, cytosine, guanine
5
Q
what are chromosomes
A
compacted DNA wrapped around protein structures (histones)
6
Q
what does DNA stand for
A
deoxyribonucleic acid
7
Q
what are genes
A
sections of DNA coiled around a protein
8
Q
what is part of the DNA structure
A
- anti-parallel dna strands
- ladder structure
- double helix
- millions of nucleotides
- sugar-phosphate backbone
- 5’-3’ and 3’-5’ directions
9
Q
who discovered DNA
A
watson, crick and franklin
10
Q
where is DNA found in prokaryotes
A
circular DNA within the nucleoid and in small rings of plasmids
11
Q
where is DNA found in eukaryotes
A
linear chromosomes within the nucleus and in mitochrondria and chloroplasts
12
Q
what happens before cells divide
A
interphase - dna must be replicated first
13
Q
what phases are in interphase in mitosis
A
G1, S, G2, mitosis
G1 is growth
S is DNA synthesis
G2 is growth and preparation for mitosis
Mitosis is PMAT
14
Q
what happens during interphase
A
cell will be growing and DNA will go through the process of DNA replication
15
Q
why is it important for DNA replication to occur in cells
A
- New cells has identical genetic information
- Required to have same information of structure and function
- Syllabus: continuity of species - making sure there are no faults within the DNA
16
Q
what enzymes are involved in DNA replication
A
helicase, DNA polymerase, primase, ligase
17
Q
what does helicase do
A
- also known as the unzipper
- separates the two DNA strands into separate DNA strands
- breaks apart the hydrogen bonds
18
Q
what does DNA polymerase do
A
- also known as the builder
- builds a complementary strand to the now separate DNA strands
- has bias - only builds in the 5’ - 3’ direction
- builds the leading strand continuously as it is in favour
- builds the lagging strand in fragments (Okazaki fragments) - continous priemrs throughout the strand
- another type of polymerase replaces the RNA primers with DNA nucelotides
- a different type of polymerase reads through all the new DNA and fixes any errors
19
Q
what does primase do
A
- also known as initialiser
- made of RNA
- the starting block for polymerase to begin
- leading strand only has one
- lagging strand has primers all along as polymerase cannot build a continuous strand
20
Q
what does ligase do
A
- also known as gluer
- seals the DNA
- sticks together the Okazaki fragments together on lagging strand
21
Q
what do the single-stranded binding (SSB) proteins do
A
- binds to the strands after the unzipping to ensure that there is no reconnection until after DNA is replicated
22
Q
what does topiomerase do
A
- attaches to the DNA to prevent supercoiling
23
Q
what are the different models of DNA
A
conservative
semi-conservative
dispersive
24
Q
what is the conservative model
A
DNA would be copied and made an identical second new molecule
25
what is the dispersive model
the DNA gets cut up into pieces and gets copied separately before being reattached with segements of botht the new and parent DNA in both strands
26
what is the semi-conservative model
the two DNA strands separate and each strand serves as a template to make two new strands and the result is one original strand and one new strand in both the DNA molecules
27
what are two aspects of DNA replication in regards to continuity of species
* genetic stability
* genetic variation
28
why genetic stability is good
producing identical DNA strands enables favourable traits to be passed on
* somatic - enables them to function correctly and keep organism alive to reproduce
* gametes - enables favourable traits to be passed to the next generation
29
why genetic variation is good
low levels of mutation are introduced - low variation
* natural selection can occur and specieis is more likely to survive changes
30
what is mitosis
the process of where one parent cell divides into two identical daughter cells with the same number of daughter cells
31
what is mitosis used for
for somatic (body) cells for growth and repair - repair of damaged tissue and replacement of old cells
32
genetic stability in mitosis
ensures the precise and equal distrubution of chromosomes to each daughter cell resulting in all daughter cells having the same chromosome number and genetic information
33
what cells fo mitosis produce
body cells
34
how many chromosomes are in humans
46 in body cells
23 in gametes
35
how many chromatids are in a cell
92 chromatids in body cells
46 chromatids in gametes
36
do cells divide all the time
no, because uncontrolled cell growth can lead to cancer and cells are programmed to know when to start and stop
37
how long is interphase and mitosis in the cell cycle
interphase - 90%
mitosis/cell division - 10%
38
what the stages of division in mitosis
I - interphase
P - prophase
M - metaphase
A - anaphase
T - telophase
C - cytokinesis
39
what happens in interphase (mitosis)
* cell replication occurs
* all the genetic information (DNA) gets duplicated
40
what happens in prophase (mitosis)
* chromatin (loose DNA) condenses into chromosomes
* chromosomes have two copies of DNA, one copy in each chromatid
* mitotic spindle fibre begin to form and extend across the cell
41
what happens in metaphase (mitosis)
* centrioles duplicate and spindle fibres form
* chromosomes line up at 'equator' each attached to a mitotic spindle fibre at the centromere
* at this point, chromsomes still have two chromatids
42
what happens in anaphase (mitosis)
* centromere is cleaved, allowing sister chromatids to be separated
* each chromatid is not a separate chromosome
* mitotic spindle fibres contract and chromosomes are pulled apart to opposite ends of the pole
42
what happens in telophase (mitosis)
* duaghter chromosomes gather at opposite ends
* mitotic spindles break down
* nucleur membrane begins to assemble
* result of two identical nuclei with chromosomes identical to one another
43
what happens in cytokinesis (mitosis)
* final separation into two cells by splitting cytoplasm
* nucleur division is complete and cell ccycle renews itself
44
what is meiosis
a type of cell division where a parent cell divides into 4 unique daughter cells
45
where does meosis occur
in sex cells (gametes)
46
how many rounds of nuclear divison is in meiosis
2 - I PMATx2 C
47
why do some cells have 46 and some have 23
reduction division
48
what are the different types of genetic variation methods of meiosis
* crossing over
* independent assortment
* random segregation
49
what happens in interphase (meiosis)
* same as mitosis
* DNA as chromatin is duplicated
* cell is growing and getting ready for division
50
what happens in prophase I (meiosis)
* chromosomes duplicate, condense, thicken and line up in homologous pairs
* crossing over occurs --> ensures genetic variation and that the inferitance is a mix of maternal and paternal genes
51
what happens in metaphase I (meiosis)
* independent assortment occurs - law of independent assortment states that the allele of one gene separates idependently of an allele of another gene --> random nature of separation of maternal and paternal chromosomes into daughter cells (even split into all cells) ---> genetic variation
* homologous chromosmes pairs line up in equatoria plate in two lines
52
what happens in anaphase I (meiosis)
* homologous pairs are pulled away by spindle fibres
* random segregation occurs - chromosomes are randomly allocated tot eh new daughter cells
53
what happens in telophase I (meiosis)
* nuclear membrance assembles around the chromosomes
* cytokinsis occurs to split the cell to produce 2 different daughter cells
54
what happens in prophase II (meiosis)
* chromosomes and spindles form in prophase II
* there is no crossing over
55
what happens in metaphase II (meiosis)
* chromosomes line up inthe middle in single file
56
what happens in anaphase II (meiosis)
* chromatids get pulled away by spingle fibres to opposite sides
* chromosomes again unergo random segregation and are randomly allocated to each new daughter cell --> law of segregation states that the two alleles of a single trait will separate randomly, meaning that there is a 50% either allele will end up in either gamete
57
what happens in telophase II (meiosis)
* nucleur membrane assembles
* cytokinesis occurs
* the two cells divide to make 4 unique daughter cells
58
what happens in meiosis I
diploid cels divides into two haploid cells and chromosomes number is halved
59
what happens in meiosis II
two cells fivide again resulting in four halpoid daughter cells
60
what is crossing over
homologous chromosomes exchnage info --> new allele combinations
61
what is random segregation
rndom distribution of chromoomes in meiosis I and chromatids in meiosis II into daughter cells
62
what is independent assortment
alleles are sorted into daughter cells independently of each other
Biology
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