Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Lvl Bio > Genetics Cell Cycle > Flashcards

Genetics Cell Cycle Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a gene?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a chromosome

A

Coiled & Condensed Euchromatin consisting of 1 DNA moleq

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

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

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is ploidy

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are NSC

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is synapsis

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe G1 phase & checkpt

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

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

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?

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

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)

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

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)

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
Q

Describe telophase

A

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
Q

What is the significance of mitosis?

A
  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
Q

What are the functions of mitosis?

A
  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
Q

Describe cytokinesis

A

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
Q

What are the 3 checkpts in cell cycle?

A

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
Q

Define meiosis

A

Process by which nucleus divides twice
producing 4 daughter nuclei, containg half no.of chromosomes of original nucleus (reduction division)

31
Q

Explain the need for reduction division

A

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
Q

What is a kinetochore

A

complex of proteins that binds to centromere & attaches spindle fibres during prophase to help separate SC

33
Q

Describe prophase 1of meiosis

A

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
Q

Describe metaphase 1 of meiosis

A
  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
Q

Describe anaphase 1

A
  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
Q

Describe Telophase 1

A
  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
Q

Describe prophase 2

A

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
Q

Describe metaphase 2

A

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
Q

Describe anaphase 2

A

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
Q

Describe telophase 2

A
  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
Q

What is the significance of meiosis

A
  • Maintain diploid state after fertilisation, fusion of gametes
  • ## Genetic variation, for natural selection & evolution
42
Q

What are the 3 ways meiosis gives genetic variation

A
  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)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions