continuity and variation

Question 1

define dna

Answer 1

stands for deoxyribonucleic acid
inside of the nucleus of the cell
contains genetic information which acts as a set of instructions for the cell and by extension the organism

Question 2

define chromosomes

Answer 2

thread like structures which are formed from dna strands in collaboration with special proteins called histones

Question 3

define genes

Answer 3

a section of dna which codes for a particular trait
for example the gene for eye colour

Question 4

define locus

Answer 4

the exact position of gene on a chromosome

Question 5

define alleles

Answer 5

the form or variant of a gene
for example the gene for eye colour may have the following alleles brown blue green

Question 6

define chromosome number

Answer 6

each species has its own specific number of chromosomes in its nucleus

Question 7

what is the chromosome number for humans

Answer 7

human somatic cells have 46 chromosomes in the nucleus
of our 46 chromosomes 23 inherited from the mother and 23 were inherited from the father
therefore we have 23 pairs
can be written as 2n where n= 23

Question 8

what are somatic cells said to be

Answer 8

all other cells besides gametes
said to be diploid as it contains the 23 pairs of chromosomes
2n

Question 9

what are gametes said to be

Answer 9

haploid cells as contain 23 chromosomes
n

Question 10

what is the cell cycle

Answer 10

a sequence of events that occurs between the start of one cell division and the start of the next cell division
cells undergo cell division when new cells need to be made

Question 11

what is interphase

Answer 11

when the cell is not dividing and is carrying out its regular functions the cell is said to be in the stage called interphase

Question 12

what is cell division

Answer 12

process by which a cell splits to form new cells called daughter cells
1st part – nuclear division where nucleus splits
2nd - cytokinesis – splitting of the parent cell cytoplasm resulting in the formation of 2 daughter cells

Question 13

what are the two types of cell division

Answer 13

mitosis
meiosis

Question 14

list four stages of mitosis

Answer 14

prophase
metaphase
anapahse
telophase

cytokinesis

Question 15

how does the cell prepare for cell division

Answer 15

during interphase when the cells get signal to divide:
chromosomes shorten and thicken becoming visible
chromosomes duplicate so that each chromosome is made up of 2 identical sister chromatids attached by a centromere

Question 16

what does mitosis produce

Answer 16

2 genetically identical diploid daughter cells

Question 17

where does mitosis take place

Answer 17

takes place in asexual reproduction and in the creation of new cells to replace old and damaged cells such as skin

Question 18

list 4 significance of mitosis

Answer 18

used in asexual reproduction
allows for advantageous characteristics of parent cell to be passed on to offspring
allows for replacement of damaged or old cells
used in growth whereby the cells number increases

Question 19

list the stages of meiosis

Answer 19

prophase 1
metaphase 1
anaphase 1
telophase 1
cytokinesis
prophase 2
metaphase 2
anaphase 2
telophase 2
cytokinesis

Question 20

what does meiosis produce

Answer 20

4 genetically different haploid daughter cells
results in the production of gametes or sex cells used in sexual reproduction for example sperm and ova in humans

Question 21

what is the significance of meiosis

Answer 21

each daughter has the haploid number of chromosomes the diploid number can then be restored at fertilisation
each daughter cell has a different combination of genes
this leads to variation among offspring which enables species to constantly change and adapt to changing environmental conditions