Chapter 9 Glossary terms

Question 1

Gonads

Answer 1

Organs that produce gametes

Question 2

Ovaries

Answer 2

Organ in females that produce eggs, ova

Question 3

Testes

Answer 3

Organ in males that produces sperm

Question 4

Gametes

Answer 4

Egg, sperm - haploid cells which fuse during fertilisation in organisms that reproduce sexually

Question 5

Zygote

Answer 5

first diploid cell formed after the fusion of two gametes

Question 6

Fertilisation

Answer 6

Fusion of a male and female gamete

Question 7

Germline cells

Answer 7

Specialised diploid cells found in the gonads that can undergo meiosis

Question 8

Somatic cells

Answer 8

Diploid body cells. All body cells except gametes

Question 9

Diploid cells

Answer 9

Cells with two sets of chromosomes (2n), one set derived from each parent. In humans the diploid number is 46

Question 10

Haploid cells

Answer 10

Cells with one set of chromosomes (n). These cells are produced by meiosis. In humans the haploid number is 23

Question 11

Gene

Answer 11

A section of DNA that codes for a protein, basic unit of heredity.

Question 12

Allele

Answer 12

Alternative form of a gene

Question 13

Genome

Answer 13

Al of the genes in a cell. Not all genes are switched on in any cell, but all genes are present. Every cell has the same genome.

Question 14

Chromosome

Answer 14

Threadlike structures made up of DNA and protein. Only visible during cell division.

Question 15

Chromatin

Answer 15

Chromosomes when not in mitosis or meiosis. Chromatin are made up of DNA and protein

Question 16

Autosome

Answer 16

Any chromosome other than sex chromosomes. Humans have 44 autosomes

Question 17

Sex chromosomes

Answer 17

Chromosomes that determine gender. In humans there are 2 sex chromosomes. Female: XX Male: XY

Question 18

Homologous pairs of chromosomes

Answer 18

Chromosomes that are matched, one set derived from the mother and the other from the father. Important for successful meiosis producing viable gametes. Each pair carry genes controlling the same trait.

Question 19

Chromatid

Answer 19

A copy of a duplicated chromosome, joined to the other copy by the centromere. Required for cell division and is produced in the S phase of the cell cycle.

Question 20

Karyotype

Answer 20

a diagram of the chromosomes, arranged in order of size, position of the centromere, and sex chromosomes displayed together.

Question 21

Binary Fission

Answer 21

Bacterial (proaryotic) cell division where one cell divides into 2 identical daughter cells

Question 22

Mitosis

Answer 22

Cell division for growth and repair of eukaryotic cells where one diploid cell divides into 2 genetically identical daughter cells

Question 23

Meiosis

Answer 23

Cell division for the production of gametes, where one specialised diploid cell can produce 4 genetically different haploid cells.

Question 24

Interphase

Answer 24

cell replication. the chromatids replicate to make a chromosome

Question 25

prophase

Answer 25

- chromosomes become visible - centrioles move to opposite poles of the cell - nuclear membrane disintegrates

Question 26

Metaphase

Answer 26

- spindles fibres attach to chromosomes - chromosomes line up along the equator 'M' is for middle

Question 27

Anaphase

Answer 27

- chromatids are pulled apart by the spindle fibres, forming 2 sets of chromosomes - 'A' is for apart

Question 28

Telophase

Answer 28

- nuclear membrane forms around the new set of chromosomes

Question 29

Cytokinesis

Answer 29

- the division of the cytoplasm that follows mitosis | - new cells are formed

Question 30

Mitosis inputs

Answer 30

1 diploid cell (2 sets of chromosomes)

Question 31

Mitosis outputs

Answer 31

2 diploid daughter cells, genetically identical to parent cells

Question 32

Meiosis inputs

Answer 32

1 specialised diploid cell in testes/ ovaries

Question 33

Meiosis outputs

Answer 33

4 haploid cells, genetically different gametes

Question 34

mitosis advantages

Answer 34

- If the conditions are suitable and stable (i.e. the environment) then this organism can produce many genetically identical offspring. Well suited to the environment. - No need for a mate

Question 35

mitosis disadvantages

Answer 35

if environmental conditions change, then the whole species is at risk of extinction. (as they are genetically identical)

Question 36

meiosis advantage

Answer 36

genetically different offspring (due to gametes produced by meiosis from 2 genetically different parents) therefore a species may be more likely to survive changing environments.

Question 37

meiosis disadvantage

Answer 37

You have to have a mate.

Question 38

crossing over

Answer 38

in prophase 1, homologous pairs can exchange genetic material resulting in genetically different gametes.

Question 39

Independent assortment of chromosomes

Answer 39

the separation of one homologous pair has no influence on the separation of another homologous pair resulting in the mixing of maternal and paternal chromosomes in gametes.

Question 40

Aneuploidy

Answer 40

resulting in one chromosome too few or one chromosome too many. It is caused by the non-disjunction of homologous chromosomes

Question 41

non-disjunction

Answer 41

is when a pair of chromosomes fails to disjoin or segregate so that 2 copies of a chromosome are present in the gamete instead of usually one copy

Question 42

Cell cycle

Answer 42

- G1, S, G2 -> interphase - mitosis = nuclear division - cytokinesis = cytoplasmic division

Question 43

Gap 1

Answer 43

- cell growth, the cell is functioning, producing proteins. -> some of these proteins will be enzymes necessary for DNA replication

Question 44

Synthesis

Answer 44

DNA replication occurs here in readiness for mitosis

Question 45

Gap 2

Answer 45

Continued cell growth and producing proteins, necessary for mitosis

Question 46

how many autosomes are there in a human ovum

Answer 46

22

Question 47

how many chromosomes in a human sperm

Answer 47

23

Question 48

Are sex chromosomes present in somatic cells

Answer 48

Yes