Topic 2 - Meiosis & Genetics Flashcards
What is it called when cells divide & increase in number
meiosis
What is a homologous pair?
human chromosomes arranged in pairs
What divisions are involved in meiosis
meiosis I & meiosis II
What are the four stages in meiosis I
prophase I, metaphase I, anaphase I & telophase I
What are the four stages in meiosis II
prophase II, metaphase II, anaphase II & telophase II
What occurs in prophase I?
chromosomes condense as the nuclear membrane breaks down. The centrioles then migrate to opposite poles as spindle fibres develop
What occurs in metaphase I?
chromosomes align along the equator in a random arrangement as the spindle fibres attach to the centromeres
What happens during anaphase I?
the spindle contracts and pulls chromosomes
Telophase I does what?
chromosomes reach opposite ends and spindle disappears
What happens during prophase II?
new spindle fibres form
Metaphase II has what happen?
chromatids arrange along the equator
During anaphase II what happens?
sister chromatids split at the centromere, going to opposite poles
Telophase II does what?
each group of chromosomes become enclosed within nuclear envelope
What is independent assortment?
production of different combinations of alleles in daughter cells due to the random alignment of homologous pairs in metaphase I.
What is the process by which non-sister chromatids exchange alleles?
crossing over
What is a gene?
a short section of chromosomes which code for characteristics
An allele is?
different form of the same gene
What is it when both alleles of a gene are the same?
homozygous
What is it when alleles of a gene are different?
heterozygous
What is a gene locus?
the position of a gene on the chromosome
A genotype is?
the genetic constitution (TT, Tt, tt)
Phenotypes are?
the outward appearance (tall, short)
Dominant alleles are?
always expressed in the phenotype of an organism
Recessive alleles are?
only expressed in the phenotype if there are two copies of the allele
