4 Genetic Inhertitance Flashcards
Describe the process and role of the cell cycle 4.2
G1 growth and replication of organelles.
S- DNA replication
G2 - cell check and repair
M - mitosis occurs then cell divides
After both G1 and G2 there is a cell cycle checkpoint.
Describe the process and role of DNA replication 4.1
DNA replication occurs in the S phase of cell division.
DNA helicase unravels the two DNA strands.
Primase binds to the unraveled DNA and initiates the DNA replication process that DNA polymerase then takes over.
DNA polymerase triggers pyrophosphate hydrolysis reactions between aligned nucleotides in the 3’ -> 5’ direction (of the template strand). This results in one long chain, the leading strand and several fragments called Okazaki fragments which make up the lagging strand after they have been joined by DNA ligase.
Eventually the whole strand is copied, this is called semi conservative replication.
Describe the process and role of mitosis and meiosis and compare and contrast the two processes. 4.3
Mitosis:
Prophase- nuclear envelope breaks down. Chromosomes condense. Spindle fibres appear
Prometaphase - structure connects to centromere which connects to spindle fibres.
Metaphase - chromatids align in metaphase plate (line in the middle of the cell).
Anaphase - chromatids are pulled to either end of the cell by the centromere due to spindle fibres contracting.
Telophase - nuclear envelope reforms around each set of chromosomes. Chromosomes decondense, spindle fibres disappear.
Meiosis:
The above steps occur twice resulting in 4 non identical haploid daughter cells instead of 2 identical diploid cells. In metaphase I (first metaphase) chromosomes align in pairs and crossing over occurs. In anaphase II it is random which chromatids go to which cell (independent assortment).
Distinguish clearly between genotype and phenotype 4.4
Phenotype means physical/ observable characteristics of an individual resulting from the interaction of genotype with the environment. Genotype means the genetic composition of an individual organism.
Explain how environmental factors have an effect on both phenotype and genotype 4.5
Diet, stress, lifestyle, illness and chemicals affecting growth can effect phenotype.
Radiation and mutagens can affect genotype.
Distinguish clearly between a gene and an allele 4.6
An allele is a variant of a gene, each person has two however there can be many.
A gene is a sequence of DNA at a specific location that codes for a specific characteristic of an organism.
Describe the different patterns of inheritance and be familiar with examples 4.7
Autosomal recessive characteristic - disease may skip generations, 2 carriers have a 25% chance of producing affected offspring.
Autosomal dominant - disease cannot skip generations. 50% chance of offspring having disease.
X-linked recessive -more likely males are affected. Can skip generations.
X- linked dominant - see autosomal dominant
Y-linked - only males affected, spread from father to son.
Explain dominance, recessiveness, co-dominance and complementation 4.8
Dominance - every person with that allele is affected.
Recessive - individual must be homozygous with both alleles to be affected.
Co dominance - two alleles may both affect phenotype as one does not dominate over the over e.g. Blood type.
Complementation- more than one gene controls a characteristic so alleles of all those genes affect the phenotype.
Describe the basis of the co-inheritance of certain traits 4.9
Some traits are often found to be inherited together. This is often because the genes are found close to each other on the same chromosome and are said to be linked. Normally the alleles are passed on together unless crossing over has occurred between them.
Draw a family pedigree according to convention from a given family history 4.10
Q
Relate genetic information from a pedigree and describe the family concerned. 4.11
M
Use genetic data to calculate probability of inheritance and recombination frequency. 4.12
G
