the study of heredity
genetics
an organism has a homozygous genotype. Its gametes always receive the same allele for a trait. Plants self pollinate
true-breeding
a characteristic of an organism
trait
individual has a heterozygous genotype. It parents had different true-breeding phenotypes for the trait.
hybrid
means the same as homozygous for a trait
purebred
segment of the dna that codes for a protein/trait
gene
alternative form of a gene
allele
alleles separate during gamete formation
segregation
sex cells (haploid)
gamete
the likelihood that an event will occur
probability
both of an individual's alleles for a trait are the same
homozygous
each of an individuals' alleles for a trait are different. Its gametes may receive 1 allele of the other
heterozygous
the trait expressed from the genotype, the physical expression of the genotype
phenotype
the alleles that an organism has. This will determine the phenotype
genotype
genes for different traits can segregate independently during gamete formation.
independent assortment
both alleles contribute to the phenotype (black feathers and white feathers on a chicken)
codominance
genes that have more than 2 alleles within the population (an individual can still only possess 2 alleles)
multiple alleles
cases in which one allele is not completely dominant over another resulting in a phenotype that is somewhere between the two in the hybrids (looks like blending occurred in heterozygous individuals)
incomplete dominance
traits produced by the interaction of 2 or more genes (produces many different phenotypes)
polygenic traits
organisms that have two identical alleles for a trait (ex. TT or tt)
homologous
(genetics) an organism or cell having two sets of chromosomes or twice the haploid number
diploid
one set of chromosomes as in gametes
haploid
a process of reduction division to create haploid sex cells.
meiosis
when homologous chromosomes exchange portions of chromatids during meiosis 1
crossing over
four chromatids in a pair of homologous chromosomes
tetrad
term that means an organism has two identical alleles for a trait
homozygous (pure breed)
term for a trait with different alleles
heterozygous (hybrid)
what is the difference between codominance and incomplete dominance?
codominance-both are present (Dalmatian)
incomplete dominance- is a mixture of both (pink flower from red and white)
what does polygenic mean?
many genes
what is an example of a polygenic trait in humans?
human eye color
what is the difference between diploid and haploid?
diploid- is homologous chromosomes, body/somatic cells.
haploid- is half the number of chromosomes, sex cells/gametes.
what is crossing over?
when the little part of a chromatid changes, all the chromosome different, from a tetrad
during what phase and what process does crossing over occur?
prophase 1/ meiosis
what is the difference between hybrid and pure breeds?
prue breeds both TT or tt, hybrids Tt.
what are Mendel's four basic principles. Briefly describe each.
1. Inheritance is determined by factor/genes. --Passed from parent to offspring.
2. Law of Dominance.-- Some alleles are dominant, some are recessive.
3. Law of segregation.-- Alleles separate during gamete formation. T/t
4. Law of independent assortment.
what assorts independently during "independent assortment?
blue eyes do not always mean blond hair.
what is the probability of tails coming up in a coin toss?
1:2
How do geneticists use the principle of probability?
by the punett square; predict possible
If a haploid number of chromosomes in an organism is 18 what is its diploid number?
36
If the diploid number of an organism is 20, what is its haploid number?
10
how many alleles for each gene are found in gametes? and in somatic cells?
gametes: 1 and somatic cells: 2
What do mitosis and meiosis have in common- both begin with dna ____;both start with _____ cells; both produce more ______.
replication; diploid; cells
In what four ways are mitosis and meiosis different? The purpose of mitosis is to produce ___/___ cells where as the purpose of meiosis is to produce ___/____ cells. Mitosis results in __(#) ______ cells where as meiosis results in __(#) ____ cells. The c
body/somatic; gametes/sex; 2; diploid; 4; haploid; same; different; crossing; divide; 1
during oogenesis, the 3 smaller cells produced are called ____ _____ and are not ______. The larger cell is the ____ and is viable.
polar bodies; viable; ovum
In males, the specific type of gametogenesis that occurs is called ___.
spermogenesis.
what is the phenotypic ratio did Mendel come up with in his F2 generation of the dihybird cross?
9:3:3:1
different forms of a gene are called?
alleles
if a tall homozygous pea plant and a homozygous short pea plant are crossed?
the recessive trait seems to disappear.
A punnett square is used to determine the?
probable outcome of a cross.
organisms that have two identical alleles for a particular trait are said to be?
homozygous
the physical characteristics of an organism are its
phenotype
a situation in which a gene has more than two alleles is known as
multiple alleles
unlike mitosis, meiosis in male mammals result in the formation of
four haploid gamete cells
to maintain the chromosome number of an organism, the gametes must
be produced by meiosis.
what happens to the chromosome number during meiosis?
it doubles
which ratio did Mendel find in his F2 generation?
3:1
During which phase of meiosis is the chromosome number reduced?
telophase 2
two pink-flowering plants are crossed. The offspring flow as follows: 25% red, 25% white, 50% pink. What pattern of inheritance does flower color in these flowers follow?
incomplete dominance
Alleles for the same trait are separate from each other during the process of?
meiosis 1
Which of the following is not one of Gregor Mendel's principles?
Crossing over occurs at meiosis.
offspring of crosses between parents with different traits.
hybrids
appearance due to genetic make up
phenotype
having two identical alleles for a given gene
homozygous