Test 4 College Biology (genetics)

Gregor Mendel
father of genetics
not a biologist
studied pea plant traits
used math to interpret his results
discovered basic pattern of genetics
Monohybrid Cross
cross of 2 purebred parental plants differing in 1 trait
Mendel’s conclusions
there are dominant and recessive traits
units responsible for inheritance occur in pairs
unit of inheritance, section of DNA that controls a trait
different forms of a gene
all the genes of an organism
We will write a custom essay sample on
Any topic specifically for you
For only $13.90/page
Order Now
physical appearance of a traits, how genotype is expressed
Genetic composition that controls a trait
genotype, 2 of the same allele (PP)
genotype, 2 different alleles (Pp)
used to map a certain trait through a family
Complete dominance
1 dominant allele; 1 recessive allele
Incomplete dominance
Heterozygotes show an intermediate phenotype(mixed)
red flower(RR) x white flower(rr) = pink flower (Rr)
no dominant allele
both traits show in heterozygotes
Multiple alleles
more than 2 alleles for a trait
alleles affect multiple phenotypes
ex. allele respoibsibe for siamese cats’ coloration pattern also affects the trait of crossed eyes
Determination of phenotype
single allele, two alleles, several genes, physical environment
expression of one gene is determined by another
ex. lab coloration (black, chocolate, yellow)
is the lab has pigment it will black or chocolate, if there is no pigment the lab will be yellow. Having pigment is a separate gene
Heterozygotes show more vigor than homozygotes
homozygotes have more harmful recessive traits
(inbreeding causes more homozygotes)
Environmental affects
Light, temperature, and nutrition can affect phenotypes
Thomas Morgan
studied fruit flies
genes and chromosomes are responsible for complex genetics that does not follow simple mendelian genetics
Linked genes
genes on the same chromosome
passed on together
(not passed on together when separated by crossing over)
Sex chromosomes
X and y chromosomes
male- XY
female- XX
all chromosomes that are not sex chromosomes
males sex chromosomes
(1 X 1 Y)
not 2 X chromosomes to cover each others bad traits (like females)
Sex-linked genes
males inherit all x-linked genes from mother(no mixing of maternal and paternal genes)
y-linked genes are passed only from father to son
Plastid and Mitochondrial genes
have their own DNA
DNA controls functions
usually inherit from mother