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A Lvl Bio > Genetics Cell Cycle > Flashcards

Genetics Cell Cycle Flashcards

(42 cards)

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1
Q

What is a gamete, somatic cell & germ cell

A

Gamete - Sperm/egg haploid cell carrying half amt of DNA & chromosomes
Somatic - any diploid cell other than those involved in gamete formation
Germ - Cell that develops into egg/sperm

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2
Q

What is a gene?

A

Inheritable & specific sequence of nucleotides on a DNA molecule coding for a RNA (tRNA,rRNA)/ polypeptide

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3
Q

What is an allele?

A

An alternative form of a gene, w different nucleotide sequences
Gene for eye colour - brown & blue pigment allele

Alleles of a gene occupy the same locus on a pair of homologous chromosomes
- occur in pairs in a diploid cell & only 2 pair is present in a gamete

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4
Q

What is a locus/loci

A

-Fixed position of a gene on a chromosome
- Alleles of a gene occupy the samerelative postion on a pair of homologous chromosomes occuring in pairs

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5
Q

What is chromatin?

A
  • Complex of DNA &proteins forming chromosomes within nucleus of eukaryotes

-ve charged DNA molq coiled around +ve charged histone proteins to give nucleosomes
- Histones made up of 8 protein subunits called octamer

Nucleosomes connected by linker DNA beads on a string form of chromatin (Euchromatin)
- Structure (euchromatin) is then coiled around 30nm solenoid (6 nucleosomes per turn)

(Not visible in light microscope but can see in electron)

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6
Q

What is a chromosome

A

Coiled & Condensed Euchromatin consisting of 1 DNA moleq

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7
Q

Describe duplicated chromosomes

A

DNA replication (doubling of mass of DNA) occurs at S phase of interphase

the 2 genetically identical sister chromatidsare held tgt at centromere
Centromere made up of repetitive DNA sequences

KINETOCHORE (complex of proteins)
binds to centromere & attaches spindle fibres during prophase to help separate sister chromatids of anaphase

DUPLICATED CHROMOSOME CONTAINS 2 highly coiled & condensed DNA moleq

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8
Q

What are sister chromatids

A

2 chromatids w exact same nucleotide sequences
- Same alleles
- Genetically identical for nuclear division
- Ensures daughter nuclei r genetically identical to maintain genetic stability after each division

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9
Q

What measures mass of DNA? NOT sets n/ 2n

A

picogram/pg
DNA is 10pg
After DNA replication 20 pg

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10
Q

What is ploidy

A

Number of sets of chromosomes
n 2n 3n NOT MASS

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11
Q

Advantages of having diploid?

A
  • Greater genetic variation, mixture of characteristics from both parents
  • If a gene of 1 chromosome is faulty,other provides normal back up copy
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12
Q

What are homologous chromosomes?

A

chromosomes with
- same length
- same centromere position
- possess genes for same characteristics
- on same corresponding loci
- same staining pattern

1 inherited from each parent

DIFFER IN
- Not genetically identical
- From diff parent
- May contain diff alleles on same gene locus, may code for diff phenotypes

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13
Q

What are NSC

A

chromtids of a pair of HC not genetically identical as from diff parent

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14
Q

What is synapsis

A

Pairing up of HC / bivalents
Occurs in Prophase 1 of meiosis

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15
Q

W

What is crossing over

A

Process of exchanging corresponding sections of genetic material between NSC of HC during prophase 1 of meiosis

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16
Q

What is a chiasma (pl chismata)

A

X shaped structure betw NSC of HC
sire where corresponding sections of NSC of HC breaks & exchanges places w equivalent portion of chromatid (crossing over)

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17
Q

Describe G1 phase & checkpt

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A

Cell growth occurs, cell builds up large store of materials like ATP
- synthesises various enzymes for S phase in DNA rep
- Synthesis of cytoplasmic organelles (eg. ribosomes, chloroplasts)

Ensures ENERGY & NUTRIENTS for mitosis to take place
DNA rep req. enzymes, cells req organelles for survival,

G1 checkpt ensures enough nutrients
Cell cannot proceed w cell div if not enough energy & materials

18
Q

describe S phase

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A

DNA REPLICATION OCCURS, cell has 2 identical copies of genome
- DNA mass doubles
- ploidy of cell unchanged
- 2 identical DNA molecules joined tgt at centromere

  • Divides parent cell’s DNA equally betw. 2 daughter cells into 2 genetically identical copies
  • Ploidy of cell remains unchanged as no new genetic info is added/reduced
19
Q

Describe G2 phase & checkpt

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A

Cell continues to build up store of energy & synthesise more cytoplasmic organelles such as mitochondria/chloroplasts/ribosomes

Serves as safety gap ensuring DNA rep has completed

  • Cell manufactures more proteins eg. histones, ribosomal proteins, tubulin
  • G2 checkpt checks for DNA dmg after DNA rep, preventing DNA mutations
20
Q

What are the purpose of Tubulin, histones & ribosomes produces in G2 phase?

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A
  • Tubulin -> Protein forming spindle fibres involved in mitosis
  • Histones -> -ve charged DNA coiled arnd +ve histones Forming chromatin organising DNA
  • Ribosomes -> synthesises proteins eg. tubulin
  • req. for protein synthesis in new daughter cells after cytokinesis takes place
21
Q

What is mitosis

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A

Process by which nucleus divides once, producing 2 genetically identical daughter nuclei each containing same number of chromosomes and the same nucleotide sequences

22
Q

Describe prophase (longest stage)

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A

1) Chromosomes condense (become visible) w 2 sis chromatids joined at centromere
2) 2 pairs of centrioles move to opposite ends of cell, forming spindle fibres across the 2 poles (forms mitotic spindle)
- nucleolus no longer visible
3) Mitotic spindle forms,
- Each centromere (pair of centrioles) -> microtubules develop, forming star shaped aster
4) Nuclear envelope disintegrates, (dissociates into small vesicles)
5) Spindle fibres attached to kinetochores bound to centromere of each chromosome -> spindle fibres move chromosomes towards centre of cell

23
Q

Describe metaphase

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A

The mitotic spindle is fully formed,
spindle fibres attached to kinetochore on centromere of each duplicated chromosome

Chromosomes aligned at equator of cell, equidistant from poles
-> facilitates equal division of chromosomes -> genetically identical daughter cells

24
Q

Describe anaphase (shortest)

Study These Flashcards
A

1) Shortening of centromere-pole spindle fibre -> Creates tension to divide centromere of chromosome

2) pole-pole microtubules lengthen -> poles move further apart in readiness for cytokinesis

3) Sister chromatids from duplicated chromosome separate & move, centromeres 1st, to both opposite poles of spindle -> daughter nuclei produced genetically identical & SC divided equally

25
Describe telophase
1) Chromatids reach respective poles, becomes chromosomes of daughter cells 2) Chromosomes uncoil & uncondense to chromatin (for cellular processes to take place) 3) Spindle fibres disintegrate 4) Nuclear envelope reforms (resume fn of nuclear membrane 1. regulate exit of RNA, 2. entry of ATP/ proteins/nucleotides) 5) Nucleoli reappear (resume fn of nucleolus 1. site of transcription of rRNA genes 2.assembly of ribomal proteins & rRNA)
26
What is the significance of mitosis?
1. Maintains genetic stability of organism - Ensures daughter cells are gentically identical to parent - As sis. chromatids are separated during anaphase, no chiasma hence no crossing over, same nucleotide sequence) 2. Maintains diploid state - Due to replication of parental DNA during interphase - DNA is doubled in interphase & returned to original after anaphase - Arrangement of chromosomes at equator ensures equal division
27
What are the functions of mitosis?
1. Growth of multicell org. - enables zygote to increase in size 2. Tissue repair & cell replacement 3. Regeneration of body parts 4. Asexual repro
28
Describe cytokinesis
Process by cytoplasm of cell divides to give 2 daughter cells w same organelles as parent Telophase & cytokinesis occur concurrently Animal:cleavage furrow appears in cell membrane Plant: Golgi vesicles line up in middle of parent cell, dusing to form cell plate, forming cell wall (Cellulose, Hemicellulose, pectin)
29
What are the 3 checkpts in cell cycle?
G1 checkpt: Checks for sufficient nutrients, if go ahead signal received, hence complete G1, S G2 & M phase, if not received, cell cycle exited, switching to G0 G2 checkpt: checks for DNA dmg after DNA rep only continues to mitosis/meiosis if no dmg, prevents mutations M (metaphase) checkpt: Checks for attachment of spindle fibresto centromeres of chromosomesbefore anaphase aka spindle assembly checkpt - Cell div stops & swtiched to G0 if spindle fibres not properly attached to kinetochore
30
Define meiosis
Process by which nucleus divides twice producing 4 daughter nuclei, containg half no.of chromosomes of original nucleus (reduction division)
31
Explain the need for reduction division
Halves no.of chromosomes from diploid to haploid,maintains diploid condition in zygotew after fertilisation, fusion of gametes. W/o reduc div, becomes tetraploid unable to survive or repro Greater genetic variation -> evolution by natural selection survival of the fittest, aloowing popn to evolve preventing extinction
32
What is a kinetochore
complex of proteins that binds to centromere & attaches spindle fibres during prophase to help separate SC
33
Describe prophase 1of meiosis
Prophase 1 1. Chromatin condenses to visible chromosomes 2. HC pair up via synapsis, (each pair = bivalent) 3. Chromosomes consist of 2 SC joined at centromere 4. Centrioles migrate to opp.ends, forming meiotic spindle 5. Nucleolus disappears, RNA transcription & ribosome assembly stops 6. Nuclear envelope disintegrates, forming pole to centromere & pole topole spindle fibres 7.Chiasma forms on NSC of HC-> crossing over (break & rejoining) corresponding sections exchanged ->Form recombinant chromosomes, new combination of allels
34
Describe metaphase 1 of meiosis
1. Spindle fibres attached to kinetochore at centromere 2. Pairs of HC align at equator of spindle in 2 rows 3. Independent assortment of HC -> random arrangement leads to genetic variation
35
Describe anaphase 1
1. Centromere to pole spindle fibres shorten 2. Pole to pole shorten 3. HC separates, havling ploidy 4. Duplicated chromosome of each pair -> maternal & paternal chromosomes of each pair
36
Describe Telophase 1
1. Chromatids reach respective poles & become chromosomes of daughter cells 2. Chromosomes uncoil 3. Spindle fibres disintegrate 4. Nuclear envelope reforms 5. Nucleoli reappear
37
Describe prophase 2
Meiotic spindle forms, between poles & pole to centromere - Centrioles move to opposite poles, forming meiotic spindle w microtubules - Spindle fibres develop, at right angles perpendicular to axis of meiosis 1
38
Describe metaphase 2
Meiotic spindle fully formed, - Duplicated chromosomes are aligned at equator of cell in 1 row(metaphase plate,equidistant from 2 spindle poles) - Random independent assortment of chromosomes -> genetic variation
39
Describe anaphase 2
Centromere to pole spindle fibres shorten Pole to pole microtubules lengthen Centromeres of duplicated chromosome divide Non-identical sister chromatids separate pulled by spindle fibres to opposite poles
40
Describe telophase 2
1. Chromatids reach respective poles becoming chromosomes of daughter cells, uncoil into chromatin 2. Spindle fibres disintegrates 3. both nuclear envelope & nucleoli reform 4. produce 4 genetically diff daughter nuclei
41
What is the significance of meiosis
- Maintain diploid state after fertilisation, fusion of gametes - Genetic variation, for natural selection & evolution -
42
What are the 3 ways meiosis gives genetic variation
1. Crossing over of NSC of HC in prophase 1 -> new recombinant alleles 2. Independent assortment of HC during metpahse 1 & anaphase 1 3. Random fusion of gametes

A Lvl Bio (24 decks)

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