mendelian inheritance 1, probability and patterns- lecture 8 Flashcards
aneuploidy
gain or loss of chromosomes which can result from nondisjunction
trisomy 21 is caused by
non-disjunction in either
Meiosis I or Meiosis II
Meiosis I non-disjunction
both homologous chromosomes are involved in the potential trisomy
Meiosis II nondisjunction
both chromosomes involved will be from just one of the homologous chromosomes (former sister chromatids)
dosage imbalance
leads to uneven numbers of gene
products, disrupting homeostasis as discussed previously with Trisomy 21
heterokaryotype
heterozygous with one normal
chromosome and one rearranged chromosome
if the number of genes on a chromosome is a predictor of the impact of extra copies of the chromosomes, why are 13 and 18 listed s the most frequent instances of non lethal trisomy rather than chromosomes 20 and 22 which are smaller
what gives the indication of the parent of origin
haploid
Haploid refers to the presence of a single set of chromosomes in an organism’s cells. Sexually reproducing organisms are diploid (having two sets of chromosomes, one from each parent). In humans, only the egg and sperm cells are haploid.
diploid
(of a cell or nucleus) containing two complete sets of chromosomes, one from each parent.
polyploidy
having whole extra sets of chromosomes
ex: selecting genes to make strawberry be bigger
autopolyploidy
examples of heterokaryotype
meiotic problems
unequal crossing over
chromosomal inversion/deletion/addition in heterokayotype
unequal crossing over
mispairing between closely related genes (like opsins) removes and adds to gene family
opsin genes
how do opsin genes lead to color blindness
problem with gene duplication
dosage imbalance
what happens in evolution to extra gene copies
gene duplication
crossing over event question
how did inheritance work prior to mendel
blending inheritance: one short parent and one tall parent equal medium size kid (wrong)
particulate interitance
you can cross 2 things and get a dominant and cross them again and get a dominant because there are always recessive genes that can come up in a generation
polygenic
governed by many separate loci
traits may be:
monogenic (encoded by single loci) or
polygenic (encoded by multiple loci)
traits encoded by one or very few loci are simple/mendelian
traits encoded by several loci are complex/qualitative
monohybrid cross
“A monohybrid cross is the hybrid of two individuals with homozygous genotypes which result in the opposite phenotype for a certain genetic trait.” “The cross between two monohybrid traits (TT and tt) is called a Monohybrid Cross.” Monohybrid cross is responsible for the inheritance of one gene
dihybrid cross
Dihybrid cross is a cross between two individuals with two observed traits that are controlled by two distinct genes
Principle of Segregation
The Principle of Segregation describes how pairs of gene variants are separated into reproductive cells. The segregation of gene variants, called alleles, and their corresponding traits was first observed by Gregor Mendel in 1865. Mendel was studying genetics by performing mating crosses in pea plants. He crossed two heterozygous pea plants, which means that each plant had two different alleles at a particular genetic position. He discovered that the traits in the offspring of his crosses did not always match the traits in the parental plants. This meant that the pair of alleles encoding the traits in each parental plant had separated or segregated from one another during the formation of the reproductive cells. From his data, Mendel formulated the Principle of Segregation. We now know that the segregation of genes occurs during meiosis in eukaryotes, which is a process that produces reproductive cells called gametes.
