Genes And Chromosomes Flashcards
What is mitosis
When a somatic (any cell that’s not reproductive) cell divides
Enables multicellular adult to arise from zygote
What is interphase
Cell growth DNA replicates
What is prophase
DNA starts to condense
Chromosomes are visible in cytoplasm
Nuclear membrane disintegrate
What is metaphase
Spindles attach to chromosomes
One chromosome per spindle fibre
What is anaphase
Sister chromatids separate at centromere, move to opposite poles of spindle
What is telophase
Spindles start to break down
Nuclear membrane reforms
Two daughter cells identical to parent cell (interphase cell)
What is meiosis
When a germ cell divides to form gametes
Daughter cells get one chromosome set - haploid all non-identical to parent
What is crossing over
Occurs between non-sister chromatids
Site of crossing over is chiasma
Chromatids break and rejoin
When does crossing over occur in meiosis
Prophase I
Allele combination can change
What is polyploidy
Condition in which cell/organism more than two sets of chromosome
What are homologous pairs
Same size, shape, make same banding pattern when stained
Same gene in same order
MAY HAVE DIFFERENT ALLELES
What is a karyotype
Complete set of all chromosomes of any living organism
Shows all homologous pairs
What is an autosome
Any chromosome other than a sex chromosome
What is a sex chromosome
In eukaryotes
Differs morphologically or in number in two sexes
Chromosomes determine sex
What are X-linked genes
Genes on X chromosome, on region non homologous to Y
What is homogametic sex
Two matching pairs of sex chromosomes
Can be homozygous or heterozygous X- X-
What is heterogametic sex
X- Y
Hemizygous for genes (only one copy of a gene as only one X)
Which stages of the cell cycle are interphase
G1 - growth
S - DNA replication
What is G2 in cell cycle
Growth, cell prepares to divide
What is the M in cell cycle
Mitosis - chromosomes partition, cytokinesis
What is a germ cell
Cell containing half the number of chromosomes of a somatic cell and able to unite with one from the opposite sex to form a new individual; a gamete
Which trait is usually inherited in fruit flies
Wild type
NOT mutant
Why were no female fruit flies white eyed
The X sex chromosome carries the gene for eye colour