Genetics exam 1 Flashcards
Mendel proposed that there are basic units of heredity passed from parent to offspring.
Particulate theory of inheritance
Genes come in homologous pairs that segregate from each other into gametes, half carry one member of the pair and half carry the other.
Mendel’s first law of segregation
G1- duplication, S- synthesis, G2- cell double checks for errors.
Interphase
Connects the sister chromatids together in the middle.
Centromere
Site on either side of sister chromatid where spindle fibers attach.
Kinetochore
Reach out and bind to sister chromatids to pull them apart.
Spindle fibers
Area between top and bottom of inner sister chromatids where tetrads form.
Synaptonemal complex.
The attachment site that holds homologous chromosomes together after crossing over.
Chiasmata
Kinetochores attach to microtubule from opposite spindle poles.
Mitosis and Meiosis II
Sister chromatids segregate to the same spindle pole.
Meiosis I
Segregation of sister chromatids results in-
Segregation of alleles.
Cross between two heterozygotes
Monohybrid cross
Cross between two individuals with two observed traits that are controlled by two distinct genes- from independent assortment.
Dihybrid
Cross between a heterozygote for two genes and a recessive for all genes.
Testcross
Take fraction of each individual and multiply them together to get a fraction of what the combined offspring between individuals would be.
Product rule
Add probability of 1st and 2nd genotype.
Sum rule
Doesn’t affect every generation, can inherit from unaffected parent, few generations affected.
Autosomal recessive
Each generation is affected, M and F are affected, can be inherited from M or F, can inherit from unaffected parent.
Autosomal dominant
Can be inherited from two unaffected parents, M affected more than F, sons can only inherit from mother; son can only inherit Y from dad.
X-linked recessive
Daughters can only inherit from unaffected fathers, affected Aa females pass 1/2 to sons and 1/2 to daughters.
X-linked dominant
Can only be passed from father to son, if Y carried allele with trait, they will be affected.
Y- linked
Mitochondria and chloroplasts; mother to offspring only, never passed on by father.
Cytoplasmic inheritance
During gamete formation, segregation of alleles, for one gene is independent of the segregation of alleles for other genes.
Mendel’s second law: law of independent assortment
Attachment of spindle fibers to one tetrad does not affect the attachment of spindle fibers to other tetrads.
Allows chromosomes to assort independently.
More than one gene influences a trait.
Polygenic inheritance
Genes can be inherited in cytoplasmic organelles that are passed exclusively through eggs; show maternal inheritance.
Mitochondria and chloroplasts
Unlinked chromosomes with genes A and B on different chromosomes will have results closer to the expected hypothesis. Unlinked chromosomes with genes A and B on the same chromosomes will have results further from expected hypothesis.
Genetic linkage
When genes are further apart on a chromosome there will be a higher recombination frequency; on the linkage map the genes will be further apart.
Recombination (crossing over)
A/a;B/b
unlinked
AB/ab
linked
Red+white=pink
Incomplete dominance
Brown+gray=brown/gray speckles, blood typed IAIB =AB
Codominance
Homozygous recessive die before birth, heterozygotes survive, and wild type survive.
Recessive lethal alleles
One gene influences more than one trait
Pleiotropic
An individual must have one dominant allele at both loci to display phenotype.
Complementation
Percentage of individuals with a given genotype
Penetrance
The extent to which a genotype is expressed at the phenotypic level.
Expressivity
An individual with an allele for a trait may not develop the disease depending on the level that it’s expressed due to expressivity.
How someone with allele doesn’t develop disease.
