DNA unit Flashcards
(95 cards)
1
Q
purines
A
Adenine
Guanine
2
Q
pyrimidine
A
Cytosine
Uracil
Thymine
3
Q
What differenciates the species if the structure of DNA is the same?
A
Genes
4
Q
Humans have ____ copies of _____ chromosomes
A
Humans have 2 copies of 23 chromosommes
5
Q
basic structure of DNA
A
Double stranded,
Anti-parallel
Double helix
6
Q
codons
A
3 lettter word (3 bases)
7
Q
nucleotide
A
it consists of..
-one sugar
-phosphate
-a base
8
Q
why do different species have different genes?
A
becuase they need to make different proteins
ex: humans need skin while mice need fur
9
Q
when does DNA replication occur
A
during the s phase before cell division
10
Q
Where does DNAreplication occur
A
In the nucleus
11
Q
why does DNA replication occur
A
To produce idendical set of DNA
12
Q
Three basic steps of DNA replication
A
- seperate the two sides of the DNA strand
- Allow new DNA nucleotides to join to the open original DNA strand
- proofread the base pairing and join up the new DNA molecule
13
Q
Enzymes
A
are proteins that are specific to the one job they do
14
Q
RNA nucleotides consists of..
A
-a sugar,
-ribose,
-a phosphate,
-a base
15
Q
Where are free floating DNA and RNA nucleotides found?
A
in the nucleus
16
Q
Why does a cell need to do apoptosis?
A
- In fetal development, the skin between the toes and the fingers need to seperate
- Cells that are genetically damaged.
- In plant cells- to defend from infections
- In mammals, damaged cells
17
Q
Why is DNA replication semi-conservative?
A
It’s semi conservaive because..
it keeps ond of the old DNA strands and forms one new strand
18
Q
What is the step 1 of DNA replication?
A
seperating the two sides of the DNA strand.
19
Q
explain STEP 1 of DNA replication
A
- Topoisomerase unwinds and lies flat the DNA strand and breaks phosphodiester bonds to prevent breakage
- Helicase breaks hydrogen bonds holding the two sides of DNA strands together.
- Stablizing proteins attach to the parental DNA strand at the replication fork to prevent the DNA strands from rejoining
20
Q
what is the step 2 of DNA replication?
A
allow new DNA nucleotides to join to exposed based on original DNA strand
21
Q
Explain the STEP 2 of DNA replication
(leading strand)
A
- Primase adds an RNA primer (consisting of a short block of RNA nucleotides (3-4))
- DNA pol III attaches to the the parental strand where there is already an RNA primer, and it attaches new DNA nucleotides to the parental strand.
22
Q
Explain the STEP 2 of DNA replication
(on lagging strand)
A
- Primase jumps forward on the parental DNA then lies down RNA primer.
- DNA pol III attaches to the RNA primer then synthesizes the new strand backwards. This continues until the pol III bumps into the previous RNA primer.
23
Q
What are Okazaki fragments?
A
The newly synthesized DNA and their RNA Primer
24
Q
What is the step 3 of DNA replication?
A
proofreading the base pairing and join up the new DNA moleules.
25
Explain STEP 3 of DNA replication
1. DNA polymerase I removes the RNA primer and allows DNA nucleotides to fill in the empty spots. It also can remove any bases that are not paired correctly.
2. Ligase joins the new DNA nucleotides together by phophodiester bonds.
26
What does DNA replication produce?
DNA replication produces 2 identical DNA strands
27
Why is DNA replication necessary
It is necessary because of the need of new cells that require cell division
28
How does the anti-parallel nature of a DNA molecule affect its ability to replicate?
Because new DNA nucleotides can only be added at the 3' end.
The new nucleotide connects to the third carbon, so on the leading strand, the DNA pol iii synthesizes continuously. However, on the lagging strand, the DNa pol iii synthesizes discontinuoulsy in okazaki fragments.
29
What phases in a cell cycle make up interphase?
G1, S, G2
30
What happens in G1?
G1 is a stage of development of growing the cell to the adult size while creating proteins and organelles. (maturing)
31
What happens in G0 stage?
Most cells don't go through mitosis immediately, so they rest in the G0 state
Adult cells do their job
ex: skin cell
32
When do cells exit the G0 stage?
When they get a chemical message to do cell division. They enter back into the G1 stage.
33
Checkpoint 1
checking for nutrients, growth factors, and DNA damage.
34
Checkpoint 2
checking for DNA replication and cell size
35
Checkpoint 3
Metaphase checkpoint
checking to see if spindle fibers have attached properly
36
How does a cell know when to stop dividing?
Through contact inhibition and anchorage dependence
37
Contact inhibition
crowed cells stop diving when they touch other cells
38
Anchorage dependence
Is when the same type of cell is anchored to another
39
What is apoptosis
programmed cell death
40
How does a cell do apoptosis
cell breaks apart into smaller pieces
then they are put in vesicles
Finally scavenger ells engulf these vesicles
41
Why are chromosomes in pairs?
because during fertilization, you get 23 chromosomes from your mom and 23 chromosomes from your dad.
42
What is Chromosome #23
chromosome #23 is called the sex chromosome because
XX = female
XY = male
43
How many chromosomes are in a somatic cell?
Somatic cells have 46 chromosomes and is diploid ( 23x2)
44
What are gamete cells?
They are sperm and egg cells which only have 23 chromosomes.
Gametes are hploid (23 x1)
45
What type of cell division produces gentically different haploid cells?
meiosis
46
What type of cell division produces genetically identical diploid cells?
mitosis
47
How is DNA found during interphase
Chromatin
48
After the chromatin condenses and coils, what does it then become?
chromosomes
49
what are sister chromatids?
two identical copies of the chromosome attached together
50
Structure of a chromosome
two sister chromatids are attached at the centromere. The kinetochore is on the the outside on the centromere; this is where the spindle fibers attach to the chromosomes.
51
What are homologous chromosomes?
is one of a matching pair of chromosomes, one from each parent, that have the same genes in the same order but may carry different alleles.
52
Interphase
cell grows, DNA replication, and continues to grow in preparation for the cell division.
53
What happens during Prophase?
1. chromatin is condensed into chromosomes
2. Nuclear membrance dissolves
3. centrioles move to opposite poles
4. Spindle fibres start to form
54
What happens during Metaphase?
1. Chromosomes line up in the centre
2. Each chromosome is attached to spindle fibres through kinetochores.
55
What happens during anaphase?
1. The sister chromatids of each chromosome are separated at the centromere.
2. The spindle fibers pull them toward opposite ends (poles) of the cell.
56
What happens during telophase?
1. Chromosomes reach the opposite ends of the cell.
2. They uncoil back into chromatin (loose DNA).
3. A new nuclear membrane forms around each set of chromosomes.
4. The spindle fibers break down and disappear.
57
What happens during (mitosis) cytokinesis?
the cell physically splits, and you end up with two identical daughter cells, each with its own nucleus and full set of DNA.
In animal cells, the cell membrane pinches in (like tightening a drawstring) to split the cell in two.
In plant cells, a new cell wall forms in the middle (called the cell plate) to divide the cell.
58
59
What is the purpose of meiosis
to divide the chromsome number in half to produce gamete cells.
60
Geneticvariation can be created in..
meiosis
61
What phase does the crossing over occur?
prophase I
62
What happens during crossing over?
homologous chromosomes exchange segments of genes to create genetic variations during prophase I
63
where does crossing over happen?
in synaptonemal complex/synapsis
64
When does law of independent assortment occur?
metaphase i
65
what happens to create law of independent assortment?
chromosomes are positioned along the centre as tetrads. Which sister chromatids goes to the right or left is random.
66
How does fertilization create genetic variation?
due to crossing over and independent assortment, each female and male will produce unique egg and sperm cells.
Which sperm and which egg will unite is random, thus creating more genetic variety
67
purpose of Meiosis i
to separate homologous chromosomes
68
purpose of meiosis II
to seperate the sister chromatids
69
what happens during prophase i
Sister chromatids condense and pair up
Then nuclear membrane disappears and spindle fibers begin to form.
Tetrads of homologous chromosomes form.
(crossing over may occur)
70
What happens during metaphase I
all 23 tetrads line up at the equator and which sister chromatis goes to the right or left side is random ( law of independent assortment)
Spindle fibers connect to the kinetochores.
71
What happens during anaphase I
The pairs of sister chromatids seperate from the tetrads as the spindle fibers pull them towards the poles
72
What happens during telophase I
Chromosomes arrive at opposite ends of the cell.
A nuclear membrane may start to form around each group of chromosomes.
The spindle fibers break down.
The cell starts to split into two cells (this part is called cytokinesis).
73
What happens during prophase ii
sister chromatids are paired up, then nuclear membrane disappears. Spindle fibers begin to form
74
What happens during metaphase ii
sister chromatids line up along the equator and the spindle fibers attach to the kinetochores
75
what happens during anaphase ii
sister chromatids are pulled to the opposite poles
76
telophase ii
one copy of 23 chromosome is now located at each centriole
nuclear membrane reforms
Then cytokinesis occurs and divides each cell into two new cells.
77
What type of point mutation does not change the amino acid?
silent mutation
78
what type of point mutation changes the amino acid to stop?
nonsense mutation
79
what type of point mutation changes the amino acid?
missense mutation
80
What mutation does deletion mutation and insertion mutation cause?
frameshift mutation
81
What is a frameshift mutation
The code for an amino acid changes because of an added or deleted base. the rest of amino acid sequence changes as well.
82
Where does transcription occur?
in the nucleus
83
Explain what happens in transciption
1. RNA polymerase attaches to the DNA promoter
2. RNA polymerase unwinds and unzips the DNA and it attaches RNA nucleotides to the 3' end of the RNA
3. RNA polymerase reaches a stop signal (termination sequence) on the DNA.The mRNA strand is released, and the DNA rewinds.
84
To process the mRNA strand what happens?
a guanine cap is added to the 5' end and a poly A tail is added to the 3' end
RNA splicing occurs where the introns are removed and the remaining exons are joined together.
85
Where does translation occur?
at the ribosome
86
What happens during translation?
1. The start codon of the mRNA attaches to the small ribosomal subunit. The start tRNA attaches to the p site. Then the larger subunit attaches.
2. The ribosome moves along the mRNA. tRNA molecules bring the correct amino acids, matching each codon (3-letter mRNA code) with an anticodon. The amino acids are linked together to form a growing protein chain.
3. The ribosome reaches a stop codon
The finished protein is released, and the ribosome detaches.
87
what is gene expression for
to control protein synthesis so that the cell can save energy by regulating which genes are used to create proteins at which time.
88
what does operon consist of?
promotor, operator and genes.
89
what is transcriptional regulation?
regulates when and how much mRNA is produced
90
What are the two types of operons?
Repressible operon and inducible operon
91
Explain how repressible operon (tryp) works
this operon is normally turned on and the repressor is not attached o the polymerase can attach to the promotor and do transciption of the genes at any time
92
93
what molecule does repressible operon produce?
tryptophan
94
how does the production of tryptophan stop?
when tryptophan molecuels in the cell build up to a certain level, they attach to the inactive repressor. When tryp attaches to the inactive repressor, it activates the repressor which attaches tto the operaator and blockes the RNA polymerase.
95
