Meisos

Question 1

Chromosome

Answer 1

Rod shaped filamentous bodies present in nucleas & cytoplasm of prokaryotic cell which carries genes

Question 2

Difference between somatic & gamete

Answer 2

Somatic cells are human body cells with:
46 chromosomes, diploid number

Gametes are sex cells with 23 chromosomes and only n

Question 3

Zygote

Answer 3

Fusion of female gamete and male gamete

Question 4

Chromosome components

Answer 4

Centromere : holds 2 chromostids
Gene: segment of DNA that codes for a trait
Chromotids : identical copies making up a chromosome

Question 5

Homologous chromosomes

Answer 5

Chromosomes that are identical in shape, size & which code genes for same set of characteristics

Question 6

Karyotype

Answer 6

Image which depicts an organisms chromosomes which determines gender & whether a person has down syndrome

Question 7

Loci

Answer 7

Genes in same position

Question 8

Importance of mitosis

Answer 8

Growth (allows zygote to produce more cell in order to grow)
Repair & replacement : allow multicellular organism maintain its tissues.

Question 9

Cytokinesis definition

Answer 9

Process of cytoplasmic division to form two daughter cells

Question 10

Karyokinesis

Answer 10

Division of nucleas

Question 11

Meisos definition

Answer 11

Cell division whereby a diploid cell undergoes 2 cell divisions & divides to form 4 dissimilar haploid cells (sex)

Question 12

Prophase 1

Answer 12

Homologous Chromosomes shorten, visible
Nuclear membrane & Nucleolus dissappear
Spindle starts to form
Chiasma from pairing of homologous pairs

Question 13

Metaphase 1

Answer 13

Homologous chromosomes line up at equator
Centromere of chromosome attaches to extended spindle fibres
Random arrangement at equator

Question 14

Anaphase 1

Answer 14

Spindles contract, shorten & pull chromosomes to opp sides of cell
Creating random assortment

Question 15

Telophase 1

Answer 15

Nuclear membrane and Nucleolus reform
Each pole has half no. of chromosomes present in original cell
Invagination of cleavage furrow deepens till cytokinesis & karyokinesis occurs to form 2 different daughter cells

Question 16

Meiosis significance

Answer 16

Process reduces diploid to haploid
Produces Gametes for fertilisation
Ensures no. of chromosomes in species stays constant over generations
Genetic variation

Question 17

Autosomes

Answer 17

22 pairs of Chromosomes which aren’t sex cells in diploid cell

Question 18

Bivalent

Answer 18

Homologous chromosomes held together by DNA cross over

Question 19

Centriole

Answer 19

Organelle in cytoplasm giving rise to spindle fibres during mitosis and meisos

Question 20

Chiasma

Answer 20

Point where crossing over takes place between chromatids of homologous pair during prophase 1

Question 21

Mitosis

Answer 21

Process of cell division where resulting daughter cells have same diploid chromosomal no. as original parent cell

Question 22

Non disjunction

Answer 22

Failure of homologous chromosome to divide leading to extra chromosome or one less chromosome in another gamete

Question 23

Spindle fibres

Answer 23

Micros tubules that form during cell division

Question 24

Gonosomes

Answer 24

Last Single pair of sex chromosomes (XX or XY)

Question 25

Significance of meoisis

Answer 25

Genetic variation Reduced genetic content by half Gametes produced for fertilisation Ensures no. of chromosomes in species remains constant

Question 26

How Genetic variation occurs

Answer 26

Crossing over Random arrangement at equator (metaphase 1 & 2) Random fertilisation

Question 27

Where does Meiosis in animals occur

Answer 27

Female: ovary Male: testis

Question 28

Where does Meiosis occur in cell

Answer 28

In animal cell: Centrosome consisting of centriole form spindle fibres that attach to chromosome during meiosis

Question 29

Fertilisation

Answer 29

Fusion of a sperm and ovum to form a diploid zygote

Question 30

Interphase

Answer 30

Phase in cell cycle where DNA replicates

Question 31

Importance of DNA replication

Answer 31

Helps double genetic material to be shared equally during cell division

Question 32

Tetrads

Answer 32

Homologous pairs carrying genes controlling same inherited traits

Question 33

Prophase 2

Answer 33

Centriole move to opp sides Nuclear membrane & Nucleolus disintegrate. Spindle fibre forms

Question 34

Metaphase 2

Answer 34

Centromeres attach to spindle fibres Single chromosomes now like Up at equator Random arrangement

Question 35

Anaphase 2

Answer 35

Centromeres split up Chromatids move to opp sides Random arrangement Spindle fibres shorten & contract & pull chromotids to opp poles

Question 36

Telophase 2

Answer 36

Nuclear membrane & Nucleolus reforms Cytokinesis occurs. 4 haploid daughter cells produced. Genetically different

Question 37

Difference in prophase 1 & 2

Answer 37

No crossing over ring prophase 2, no bivalent Chromosome have a patched appearance in prophase 2

Question 38

Metaphase 1 & 2 differences

Answer 38

1: pairs of chromosomes align at equator but 2: single pairs align

Question 39

Anaphase 1 & 2 differences

Answer 39

2: split centromeres

Question 40

Telophase 1 & 2 differences

Answer 40

2: unreplicated chromosome / single stranded 2: 4 haploid daughter cells that are genetically different but 1: 2 identical daughter cells

Question 41

Difference between meiosis and mitosis

Answer 41

Mitosis is for somatic cells and meiosis is for gametes (site) Mitosis is for growth meiosis is for formation of haploid Gametes Mitosis makes 2 identical cells and meiosis makes 4 genetically different haploid cells Mitosis have 1 division and meiosis has 2

Question 42

Variation importance

Answer 42

Forms raw material for natural selection Increases survival chance Creates favorable features and conditions

Question 43

Causes & consequences of non - dysjunction

Answer 43

Spindle fibres fail to separate during meiosis One pair of homologous chromosome fail to separate in anaphase 1 or replicated chromosome does not separate & move into different cells in anaphase 3 2 of 4 gametes receive extra copy of affected dna 2 of 4 chromosomes lack dna

Question 44

Trisomy

Answer 44

Non dysjunction in meiosis 1 resulting in 21 down syndrome

Question 45

Characteristics of someone with down syndrome

Answer 45

Small eyes Flattened nasal bridge Protuding tongue Broad neck Epicanthic fold

Question 46

Cause of abnormal chromosome count

Answer 46

Homologous pairs fail to separate in meiosis 1 Or replicated chromosomes fail to separate in meiosis 2

Question 47

Types of nondisjunction

Answer 47

Trisomy (3 chromosomes on set 21) Monomy 23 (has 1 chromosome in set 23)