Cell division, Genetics and Inheritance

Contents of the nucleus

nuceoli and genes

Function of the nucleus

control cellular structure, directs cellular activities and produces ribosomes

Define alleles

alternative versions of a gene

Define homozygous and heterozygous alleles

Heterozygous - have different information for a trait

Homozygous - have identical information for a trait

Describe somatic cell divison

replicates cells to replace dead and injured cells during tissue growth and occurs through cytokinesis and mitosis

Describe reproductive cell division

produces gamete cells required for next generation through meiosis which occurs in the testes and ovaries (gonads)

How does genetic variation occur

mutations introduce new alleles, gene recombination shuffles alleles and gene flow transfers genes between populations

Define cancer

the group of diseases which results from uncontrolled or abnormal cell proliferation

Difference between malignant and benign tumours

malignant tumours undergo metastasis whereas benign tumours do not

Name the type of cancer that arises from epithelial tissue, melanocytes, lymphatic tissue and leukaemia

Epithelial tissue - carcinoma

Melanocytes - melanoma

Lymphatic tissue -

lymphoma

Leukocytes - leukaemia

3 causes of cancer

environmental agents, viruses, genes

Define inheritance

the passage of hereditary traits from one generation to another

Define genetics

the branch of biology that deals with inheritance

Define Genotype

the genetic makeup of an individual e.g. Pp

Define phenotype

the physical characteristics determined by the genotype and environment e.g. blonde hair, blue eyes etc

Define mutation

a permanent heritable change in a gene that causes it to have a different mutation effect than it had previously

Explain dominant and recessive alleles

dominant alleles are always expressed or evident in a person e.g. DD or Dd, whereas recessive alleles are only expressed when there is no dominant allele present e.g. dd

Explain autosomal dominant

Pp, caused by mutation of a single gene on a chromosome, one parent will have 50% chance of their child having the disease e.g. huntington's disease

Explain autosomal recessive

pp, caused by mutations of two gene pairs on a chromosome, e.g. cystic fibrosis

Explain x-linked recessive

caused by mutation on the X chromosome, more common in men as they only have one X chromosome

Define multiple allele inheritance

genes with more than two alternate forms e.g. allele coding for blood type

Define complex inheritance

most inherited traits are not controlled by one gene by by the combined effects of 2 or more genes and environmental factors e.g. hair colour, skin colour

Difference between autosomes and sex chromosomes

autosomes are any chromosomes other than sex chromosomes and sex chromosomes are the 23rd pair (XX and XY)

Difference between trisomy and monosomy

trisomy involves an extra chromosome resulting in 47 altogether e.g. down syndrome whereas monosomy involves an extra chromosome resulting in 45 altogether e.g. turner syndrome