meiosis/mitosis test
What occurs during Meiosis but not mitosis?
Homologus chromosomes pair up
Cell biologists play an important role in research into disease, fertility,
evolution and many other areas of science. Compare and contrast the processes of spermatogenesis and oogenesis.
both result in haploid cells/gametes
both have cell growth «before meiosis»
both involve «two divisions of» meiosis
both are stimulated by hormones
The biological insights of Mendel and Darwin in the 19th century remain important to this day.
Discuss the role of genes and chromosomes in determining individual and shared character features of the members of a species.
mutation changes genes/causes genetic differences
alleles may be dominant or recessive
dominant alleles determine trait even if recessive allele is present
all members of a species are genetically similar/have shared genes
Describe the different cell types in the seminiferous tubules that are involved in the process of spermatogenesis.
spermatogonia mature and divide «by mitosis» into primary spermatocytes "2n"
Cells go through a repeating cycle of events in growth regions such as plant root tips and animal embryos. Outline this cell cycle.
consists of four phases: prophase, metaphase, anaphase, telophase
DNA replicates in the S phase
cell growth
mitosis is the division of a nucleus to produce two genetically identical daughter nuclei
Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.
meiosis reduces a diploid cell into (four) haploid cell(s);
(during prophase I) homologous chromosomes pair up, this is known as synapsis;
metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell;
(anaphase I) (homologous) chromosomes separate and move to opposite poles;
(telophase I) chromosomes reach poles and unwind
(prophase II) chromosomes (condense and) become visible, new spindles form;
(metaphase II) chromosomes line up at the centre of the cells/equator;
(anaphase II) sister chromatids separate;
(telophase II) chromatids reach the poles and unwind;
Outline the processes that occur during the first division of meiosis.
consists of) prophase, metaphase, anaphase and telophase;
chromosome number halved/reduced/(diploid) to haploid;
homologous chromosomes pair up/form a bivalent
crossing over between non-sister chromatids
nuclear envelope breaks down (at end of prophase/start of metaphase)
f. bivalent pairs move to align on equator/cell centre
g. attachment of spindle fibres
h. (homologous) chromosomes separate/pulled to opposite poles in anaphase;
i. nuclear envelopes reforms
Prior to cell division, chromosomes replicate. Explain the process of DNA replication in prokaryotes.
a. DNA replication is semi-conservative
each molecule formed has one new strand and one from parent molecule;
helicase uncoils DNA
helicase separates the two strands by breaking hydrogen bonds between bases
RNA primase adds primer
DNA polymerase III binds to/starts at (RNA) primer
DNA polymerase (III) adds nucleotides/bases in a 5’ → 3’ direction;
bases according to complementary base pairing / A–T and C–G;
the leading strand is built up continuously (towards the replication fork);
the lagging strand built up in Okazaki fragments;
DNA polymerase I removes RNA/primers and replaces them with DNA
ligase seals gaps between fragments
Describe the process of spermatogenesis leading to the production of four sperm cells in a human male
in the seminiferous tubule
spermatogonia grow
primary spermatocyte carries out the first division and secondary spermatocytes carry out the second division
meiosis produces haploid cells/spermatids
spermatids differentiate into sperm cells ; develop tail or flagellum