mitosis meopsis

Different cell cycle phases

G1, S phase, G2, M phase, cytokinesis

What happens in G1 and G2

organelle synthesis

What happens in the S phase

Semiconservative DNA replication

How is DNA arranged within a chromosome [3]

• DNA is coiled around protein histones

• By ESA as DNA is negatively charged and histories is positively charged

• Form super coils that fold further to form a chromosome

What must happen to genetic material during interphase for chromosome to be visible [2]

• DNA replication

• followed by spiralling and condensing of chromosome

Structure and role of centromere [5]

• non-coding DNA consisting of tandem repeat sequence found along a chromosome

• allow sister chromatids to adhere to each other

• allow kinetochore proteins to attach

• and subsequently spindle fibres attach to kinetochore so

• allow aligner of chromosomes at equator during metaphase

• sis chromatids/HC can be separated to opposite poles

Structure of HC [2]

• A pair of chromosomes one paternal one maternal with same genes but diff alleles at corresponding loci

• similar in shape, size, centromere position and staining pattern

what is a somatic diploid cell [3]

• contain 2 complete sets of chromosomes existing in homologous pairs

• where each of the chromosome of the pair comes from either parents

• 2n

what is a gametic haploid cell [3]

• contains only one complete set of chromosomes

• contain 1 homologue from each HC pair

• n

what happens during fertilisation in terms of cells [1]

fusion of haploid sperm and haploid egg to from a diploid zygote

how does meiosis lead to the formation of 4 haploid cells [2]

• 1st meiotic division, diploid parents undergo separation of HC at anaphase 1

• 2nd meiotic division, sister chromatids separated at anaphase 2

mitosis definition

form of nuclear division producing 2 daughter nuclei with identical sets of chromosomes as parental cell nucleus

meiosis definition

form of nuclear division in sexually reproducing organisms that produce haploid daughter nuclei with half chromosome number of parents

the need for tight control of mitotic call cycle [4]