genes Flashcards
what is chargaffs rule
states the amount of guanine is equal to the amount of cytosine and the amount of adenine is equal to the amount of thymine
what does diploid mean
having two haploid sets of chromosomes in each cell
what are homologous pairs
a pair of chromosomes that have the same size, shape and genes at the same locations.
what is a phenotype
the expression of a genotype
what is a genotype
the combination of alleles for a particular trait/ i899999999999999999999999
what is a gene
a section of coding DNA that codes for a protein. a hereditary unit
where are genes located
in chromosomes
what is an allele
different variation of a gene
what is a genome
the sum of an organisms DNA and genetic material
What is the DNA structure
double helix made of sugar phosphate backbone and nitrogenous bases (A,C,T,G)
what does DNA do
code for proteins and directs how cells, tissues and organisms function
what is the base pairing rule
A and T. C and G
what is a loci
refers to he location of a gene on a chromosome
how many pairs of chromosomes are there in the human body
23
what are autosomes
The 22 matched pairs of chromosomes
what are sex chromosomes
determine sex of an individual. X or Y
what is a karyotype
organized set of chromosomes in a cell
how is a karyotype organized
largest to smallest autosomes then sex chromosomes
what is trisomy
an extra chromosome
what is monosomy
one less chromosome
trisomy 21
down syndrome
what is klinefelter syndrome
XXY
what is turner syndrome
X
homozygous
identical pair of alleles
heterozygous
different alleles
complete dominance
one allele masks the other
incomplete dominance
heterozygous creates third blend
codominance
both dominant alleles are expressed
crossing over
homologous pairs exchange segments at chiasma to create more diversity
non-disjunction
homologous pairs not splitting at centromere properly in anaphase 1 or 2
independent assortment
each pair aligning at middle and separating into individual gametes to increase diversity.
How many cells does meiosis create
4 cells with half the number of chromosomes as starting cell
how many divisions occur in meiosis
2
prophase 1
growth
metaphase 1
homologous pairs align at equator of spindle. Nuclear membrane disappears
anaphase 1
spindle fibers retract towards poles. pairs separate and move to opposite poles
telophase 1
nuclear membrane reforms. cytokinesis will occur at the same time.
prophase 2
nuclear membrane breaks down, spindle fibers reform and connect to chromosomes.
metaphase 2
paired chromosomes align at equator
anaphase 2
centromeres divide and chromatids pulled to opposite poles
telophase 2
spindle breaks down. membrane reforms. cell splits
