Meiosis Flashcards
Why are haploid present
To maintain constant number of chromosomes in an adult the number of chromosomes must be halved at some stage
What does a diploid consist of
Has two complete set of chromosomes one set provided by each parent
What is meiosis in general terms
Homologous pair of chromosome separate into each daughter cell these chromatids then split one chromatid into each daughter cell
What is first didvision
Homologous chromosomes wrap around each other and portions of chromatids may be exchanged in crossing over the homologous pairs separate one into each daughter cell
What is second mieotic divison
Chrimatids move apart at the end of meiosis four cells have usually been formed each with 23 chromosomes
What is a gene
A length of dna that codes for a polypeptide
What is a locus
A position of a gene in a chromosome or dna
What is an allele
One of different forms of a gene
What is a homologous chromosome
A pair of chromosome that have same gene loci one from mum and one from dad
What is independent segregation
And how does it cause variation
The chromosomes pair line up randomly one pair of each chromosome will go to different daughter cells.
Which one of the chromosome goes to which of the daughter cells in random so combo of alleles is different to the parent genetic make up leads to variation
How does variety appear
Member of the homologous pair has exactly the same gene which determine the same characteristic but there are allele the independent assortment which f chromosomes therefore produce new genetic variation
What will the gametes do after wards
They will be genetically different and they randomly fuse at fertilisation to form diploid state so random fusion create variety in offspring
What are the steps for recombination
Chromatids of each pair become twisted around another
Tension is created which may make some portions of chromatids break off
Broken portions may recombine with chromatids of its homologous pair
Equivalent portions of chromatids are exchanges
New genetic combo of maternal and paternal alleles are produced
