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Biology A Level Year 12 Ms Felfeli > Mitosis, Meiosis and Mutations > Flashcards

Mitosis, Meiosis and Mutations Flashcards

1
Q

what are the three type of point mutations?

A
  • substitution
  • addition
    -deletion
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2
Q

what happens in substitution?

A

-a DNA nucleotide is substituted for another/different base
-sometimes it can have no impact but others can have catastrophic consequences for the primary, secondary and tertiary structure for the protein
-due to the degenerate nature not all mutations are sever

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2
Q

what happens in addition?

A

-an extra DNA nucleotide may be added
-this impacts all subsequent triplets will be effected - all amino acids right of the addition will be incorrect FRAMESHIFT to the right
-new forms of alleles arise form changes of existing alleles

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2
Q

Mutagens:

A

mutations appearance can be increased by mutagens such as:
- x-rays
-gamma rays
-nicotine
-benzine
-caffeine
-uv light

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3
Q

what happens in deletion?

A

-a DNA nucleotide is removed
-all subsequent triplets are effected so polypeptide chain will a different primary structure/ order of amino acids - FRAMESHIFT to the left

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3
Q

Semi-conservative replication:

A

two strands separate - H bonds break between the complimentary bases - DNA helicase
DNA nucleotides line up with complimentary bases - H bonds form
Bonds between DNA nucleotides - phosphodiester due to condensation reaction - enzyme DNA polymerase
both strands of the DNA are used as a template

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3
Q

why is it called semi-conservative replication?

A

because each new DNA molecule contains one of the original strands

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3
Q

experiment carried out:

A

they based their work on three principles:
- all bases in DNA contain nitrogen
- nitrogen has two isotopes 14N and 15N
- Bacteria will incorporate nitrogen from their growing medium too any new DNA they make
They grew E.coli on a medium containing the heavy isotope of 15N for many generations so “all” the DNA was “labelled” with heavy N
the bacteria was transferred to a medium containing the lighter isotope of 14N for 1 or 2 or 3 generations

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4
Q

METAPHASE:

A

chromosome structures line up in single file along the equator of the cell, centrioles produce protein fibres called spindle fibbers - extend and attach to the centromere

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4
Q

what is conservative replication?

A

it’s the method of replication when the DNA is copied anew one daughter cell is made of entirely new material

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4
Q

why mitosis?

A

replace dead/damaged cells
growth in the number of cells so organisms can get bigger
asexual reproduction - plants - quick, one parent, alleles identical, maximise optimal environmental factors

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4
Q

what is the centromere:

A

a protein that holds together two chromatids

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4
Q

outcome of mitosis:

A

two genetically identical daughter cells produced

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4
Q

INTERPHASE:

A

G1 phase - DNA helicase, DNA polymerase, DNA nucleotides, phosphates, deoxyribose, bases, ATP
S phase - synthesis DNA molecule replication - semi-conservative replication
G2 phase - cytoplasm, organelles, phospholipids –> membranes, ATP
At the end of G2 in preperation for mitosis centrioles mature and migrate to either poll of the cell

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4
Q

three main stages of the cell cycle:

A

interphase
mitosis
cytokinesis

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5
Q

MITOSIS:

A

stage of the cell cycle where chromosome structure is visible - protein synthesis

5
Q

PROPHASE

A

chromatin shorten and thicken - hyper coil forms visible chromosome structures, nuclear membrane disappear

5
Q

ANAPHASE:

A

spindle fibres contract pulling on genetically identical sister chromatids to either pole - the centromere has split

5
Q

TELOPHASE:

A

chromatids unwind, they get long and thin again and become chromatin again, the nuclear envelope reforms around the chromatin at each pole the cell membrane folds inwards at the equator - cleavage line

5
Q

CYTOKENISI:

A

two genetically identical daughter cells they have the same genetics as each other and parent cells

5
Q

Cancer:

A

cancer is due to uncontrolled cell division and occurs when the rate of cell multiplication is faster than the rate of cell death. Cancer is caused by mutations to the genes involved in regulations os mitosis and the cell cycle

5
Q

mitotic index =

A

the number of cells undergoing mitosis/ total number of cells visible
higher mitotic index the faster mitosis occurs

6
Q

why meiosis?

A

to maintain the chromosome number in the adults of a species that number must be halved at some point
genetic variation - exchange of alleles

7
Q

INTERPHASE:

A

replication of DNA

8
PROPHASE 1:
chromosomes shorten and thicken to become visible, centrioles migrate to the poles of the cell. Homologous pair of chromosome pair up and exchange alleles in a process called crossing over. Those pairs are called Bivalents, crossing over forms chiasmata. Crossing over is completely RANDOM - 1st opportunity for genetic variation
9
METAPHASE 1:
chromosomes line up on the equator but they do so in their bivalent pairs, spindles attach to the centromere
10
ANAPHASE 1:
2nd opportunity for genetic variation. Independent segregation of chromosomes. The centromere doesn't split when the chromosomes migrate and the spindles contract - the whole chromosome migrates to each pole - this process is completely RANDOM
11
TELEPHASE 1:
chromosomes start to unwind to become long and thin turns into chromatin, the membrane begins to fold inwards, nuclear envelope starts to form
12
CYTOKYNESIS 1:
get two genetically different daughter cells that stay quite close together
13
PROPHASE 2:
chromosome structures shorten and thicken and become visible, nuclear envelope disappears and centrioles migrate to poles
14
METOPHASE 2:
chromosomes line up in a single file on the equator and spindle fibres attach to the centromere
15
ANAPHASE 2:
spindle fibres contract and the centromere splits and one of each chromatid is pulled to either pole - independent segregation o chromosomes, 3rd opportunity for genetic variation, completely RANDOM
16
TELOPHASE 2:
genetic material unwinds becomes long thin chromatin, nuclear envelope reforms, membrane folds inwards to form cleavage line
17
CYTOKYNESIS 2:
cytoplasm and organelles are split and the cell membrane forms two new cells
18
at the end of meiosis:
- 4 cells - tetrad - not genetically identical to each other or parent cell -half genetic material - haploid
19
Non-dijunction:
non-disjunction is failure of chromosomes to separate and segregate into daughter cells - something is wrong with the spindle fibres non-disjunction may occur during meiosis 1 or 2 abnormal number of chromosomes may be a result
20
Binary Fision:
- the bacterium before binary fission is when the DNA is tightly coiled - the DNA of the bacterium has uncoiled, circular DNA, both strands attach to the cell membrane, DNA helicase breaks the H bonds between the strands, DNA nucleotides sit in complimentary base pairs, opposite both strands - both templets, DNA polymerase joins the nucleotides together - phosphodiester bonds due to condensation reactions, any plasmids will replicate, phospholipids, cell wall, membrane, ribosome all increase -the DNA is moved to the separate sides of the bacterium as the membrane increases -the growth of new cell wall begins to separate the bacterium -the new cell wall fully develops - membrane folds inwards resulting in complete split -DNA will tightly coil, ribosomes and plasmids sit between bacterium
21
Lytic cycle:
-virus attaches to the surface of the cell using attachment proteins, lipid envelope fuses with the cell membrane and the genetic material enters the cell -RNA replication using cells own RNA nucleotides -virus RNA holds information on how to construct the protein capsid and antigen/attachment proteins -cell does translation (ribosomes and RNA) and constructs the viruses proteins - reconstructed viruses inside the cell - pinch off and leaves the cell and the virus takes the cell membrane t form its lipid envelope - eventually the cell bursts
22
Lysogenic cycle:
lysogenic cycle is the lytic cycle with one additional step: reverse transcriptase enzyme will makes single-stranded viral DNA from viral RNA viral double-stranded DNA done by cells goes into the nucleus it integrates into the DNA of cells - there permanently when cells undergo mitosis it replicates viral DNA as well can remain dormant until the environment is suitable for virus to reproduce

Biology A Level Year 12 Ms Felfeli (6 decks)

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