Eukaryotic chromosome
chromosome with DNA and protein
gene
a heritable factor that controls a specific characteristic
allele
one specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene
genome
the whole of the genetic information of an organism
46
number of chromosomes in humans (23 homologous pairs)
gene mutation
a random change in the code within genetic material
sickle cell anemia
GAG mutates to GTG; valine coded for instead of glutamic acid; cells form sickle shape and don't carry oxgen as well and clog in capilaries
substitution mutation
one base is substituted for another in the DNA
3 results of substitation mutation
1. not in a coding area; no change in protein
2. in coding area but still codes for same amino acid so no change in the protein
3. in coding area; codes for different amino acid; changes the protein
meiosis
a reduction division of a diploid nucleus to form haploid cells (cell division resulting in sex cells)
homologous chromosomes
chromosomes that code for the same gene although there will be coding for different alleles (there are 23 pairs of homologous chromosomes in humans)
haploid
1n; only one chromosome of a homologous pair seen; sex cells
diploid
2n; both homologous chromosomes of a pair seen; body cells
crossing over
the exchange of alleles among homologous pairs during late prophase and metaphase of meiosis 1.
meiosis process
process in which homologous chromosomes pair then split apart during a first cell division; then lining up and splitting of sister chromatids to form 4 haploid sex cells. (know the stages of this process)
non-disjunction
failure of chromosomes to properly split apart during meiosis resulting in an extra chromosome in one of the daughter cells. Can be caused by failure of sister chromatids to split in anaphase II or failure of the homologous pair to split in anaphase 1.
Downs syndrome
condition resulting in nondisjunction resulting in an extra 21st chromosome (trisomy 21)
karyotypes
a photograph of chromosomes taken during metaphase of mitosis and then arranged by size and strucure to show sex and any abnormalities in chromosome number
2 methods of collecting cells for karyotype
1. amniocentesis
2. chorionic villus sampling
amniocentesis
collection of a cell from amniotic fluid by use of a needle
chorionic villus sampling
geting a cell sample from finger like projections of the placenta into the uterine wall
XX
female sex chromosomes
XY
male sex chromosomes
Gregor Mendel
father of genetics; studied pea plants
genotype
the alleles of an organism; usually represented by 2 of the same letters BB, Bb., bb, etc.
phenotype
the characterisics of an organism ex: number of fingers on each hand
dominant allele
an allele that has the same affect on the phenotype whether it is present in the homozygous or the heterozygous state (shown as a capital letter in genotype)
recessive allele
an allele that only has on affect on the phenotype when present in the homozygous state (shown as lower case in genotype)
codominant alleles
pairs of alleles that both affect the phenotype when present in a heteroxygote (the terms incomplete and partial dominance are no longer used)
locus
the particular position on homologous chromosomes of a gene
homologous
having two identical alleles of a gene
heterozygous
having two different alleles of a gene
carrier
an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele
test cross
testing a suspected heterozygote by crossing it with a known homozygous recessive
multiple alleles
having more than two alleles possible for a gene; for example the ABO alleles of blood
ABO blood groups
example of multiple alleles and codominance
Punnett Square
a diagram used to show all of the possible combinations of alleles for a given trait given a set of parents
sex chromosomes
the 23rd pair of chromosomes; determine sex of the individual
sex linkage
a genetic trait that has its locus on the X or Y chromosome (ex haemophilia, color blindness)
colorblindness
sex linked trait; inability to distinguish between certain colors (often red and green); on X chromosome
haemophilia
disorder causing blood to not clot properly
pedigree
a chart or record of an organisms ancestry
square
shape of a male in pedigree
circle
shape of a female in pedigree
shaded
homozygous recessive in pedigree
horizontal line
line showing male and female who have offspring in pedigree
vertical line
line showing a relationship between parent and offspring in a pedigree
sex linked carrier
a female heterozygous individual for a given genetic sex linked trait
monohybrid cross
a cross showing alleles of only one gene