Studied by 101 peopleDolly sheep experiment procedure & significance
used cytoplasmic and nuclear donor of nucleus and mammary cells to create the first instance of successful mammal cloning
idea of preformation/humunculus
17th and 18th century idea that humans develop from miniature versions of themselves that are either in the egg (ovist), or sperm (spermist) - now discredited (obviously)
blending hypothesis
outdated theory that traits from each parent were blended onto offspring
why did Mendel use peas
cross-breed them easily, multiple characters, short lifespan, big sample size (high reproductive rate & self fertilization)
how did Mendel cross fertilize pea plants?
cut off anthers of one flower, transfer anthers from another flower into the original flower’s stigma, plants seeds in peas
7 characters studied by Mendel
height, flower color & position, seed color & shape, pod color & shape
true breeding
when individuals with a particular trait are bred together and offspring have the same trait as parents (trait is homozygous)
monohybrid cross
A monohybrid cross is a genetic cross between two individuals that differ in only one trait. Single gene/allele from each parent.
how did Mendel discover recessive, and heterozygous traits?
bred two true breeding parents of different parents, found all offspring had one trait, and amongst the offspring self fertilizing, the more common trait was present 3:1
Particulate theory of inheritance
Mendel - hereditary traits are determined by discrete units called genes, which are passed from parents to offspring. Genes are individual and do not blend in reproduction
genotype vs phenotype
Genotype refers to the genetic makeup of an organism (allele combination), phenotype are physical characteristics.
gene vs allele
A gene is a segment of DNA with specific instructions for building a protein. An allele is a variant form of a gene.
homozygous vs heterozygous
homozygous two identical alleles. heterozygous two different alleles
dominant vs recessive
dominant masks recessive. dominant is expressed if one allele is present, recessive is only expressed if both alleles are recessive.
somatic cell vs gamete
A somatic cell is any cell in the body except for reproductive cells (diploid & mitosis). Gametes are reproductive cells (gamete and egg, haploid & meiosis).
diploid vs haploid
diploid cells have two sets of chromosomes, one from each parent. haploid cells have one set of chromosomes.
law of segregation and what it tells you
two alleles for a given gene segregate away from each other during the production of gametes (think of diploid to haploid) - tells you that the segregation is random
what are Punnett squares and why is it important that we understand how to set them up?
we can predict offspring traits and better understand genetic inheritance
Test Cross
Dominant phenotype individual, cross with a recessive phenotypic individual to know if the dominant phenotypic individual is homozygous or heterozygous
goal of mitosis
diploid parent cell forms two diploid daughter cells (daughter cells look genetically identical)
Which cell cycle phase is the shortest?
Mitosis
Interphase includes…
G1, S, G2
S phase
DNA replication
G1 & G2 Phase
cell growth, protein synthesis, checkpoints (G1 checks mitotic issues, G2 checks replication errors)
how long does a normal cell go through the cell cycle typically?
approx. 24 hours
linked assortment hypothesis
certain genes located close to each other on the same chromosome tend to be inherited together (wrong)
independent assortment hypothesis
different PAIRS of genes (alleles) separate independently into gametes during meiosis. (correct)
Dihybrid cross
breeding including two different traits (genes) that are located on separate pairs of homologous chromosomes
dihybrid cross heterozygous ratio
9:3:3:1
genetic polymorphism
refers to the presence of multiple variations (alleles) of particular genes within a population
wild type allele criteria (4)
most prevalent alleles, promotes reproductive fitness, DOES NOT MEAN DOMINANT, there can be more than one wild type allele
Mutant alleles
non wild type alleles, commonly recessive, can be dominant (gain of function allele, dominant-negative allele)
when are most mutations for alleles usually produced?
during DNA replication (common but many are inconsequential)
what are some reasons to why do mutations cause a lack of function?
blocks activity (screws up as a protein), blocks folding, blocks transcription of a particular enzyme,
gain of function allele
type of mutant allele that results in a gene having a new or enhanced function when compared to the wild type allele
dominant negative allele
mutant allele that can negatively effect the ability of the wild type allele to function
polydactyly is an example of
a dominant allele mutation that exhibits incomplete penetrance
incomplete penetrance
individuals carrying a specific genetic mutation do not always express the expected phenotype
expressivity
the range of a allele (gene’s) phenotypic expression in an individual
interphase
growth, DNA replication, cell functions (cells spend most of their time here)
chromosomes
condensed DNA and proteins
centromere
part of a chromosome where sister chromatids are held together
chromatids
strands of replicated chromosomes
Prophase
(before) nucleus is present, chromosomes are condensing, nuclear membrane/envelope is beginning to break down, spindle fibers/microtubules begin to form and extend from opposite ends of the cell, centrioles present
Metaphase
(middle) chromosomes align at the middle of the cell, spindle fibers attach to chromosome’s (two sister chromatids) centromeres (kinetochore region). Metaphase plate forms, bivalent attachment occurs
Anaphase
sister chromatids separate and are pulled to centrioles by spindles
Telophase
spindles break down, nuclei reforms
sister chromatid vs homologous chromosome
sister chromatids are like identical twins of a single chromosome (same color and shape) while homo chromosomes are not identical, but work together (similar shapes, usually different colors unless it’s after replication)
centriole
organelles commonly found on opposite ends of the cell that contain microtubules
centrosome
contains a pair of centrioles, organizes microtubules
kinetochore
protein structure that forms on centromere region of a chromosome
metaphase plate
tells where cytokinesis will occur later
bivalent attachment
proper and stable attachment of homologous chromosomes to the microtubules of the spindle
Cytokinesis
cleavage furrow forms and cytoplasm is eventually divided into two and two daughter cells are formed that are genetically identical to parent
actin’s role in mitosis
animal cell protein that is responsible for forming a contractile ring (cleavage furrow process) in cytokinesis
how is cytokinesis different in plant cells?
due to a rigid cell wall, a cell plate is formed instead of a cleavage furrow to separate two daughter cells
After replication, a homologous pair of chromosomes (different colors but similar shape), turn into
two sets of homologous chromosomes that are each similar in color, and each contain two sister chromatids
s phase
DNA replication & metabolic activity
prophase 1
chromosomes condense, thicken, align with homologous pairs - CROSSING OVER occurs
metaphase 1
chromosome pairs align at middle of cell
anaphase 1
spindle fibers pull away chromosome pairs to opposite sides of the cell
telophase 1
nuclear envelope reforms, revealing two distinct nuclei
prophase 2
spindles begin to form in each distinct nuclei
metaphase 2
chromosomes align in the middle of each distinct nuclei
anaphase 2
sister chromatids are pulled to opposite ends the cell by spindle fibers (each chromatid is now a referred to as a chromosome)
telophase 2
nuclei reforming, two cells divide into four cells
karyokinesis vs cytokinesis
karyokinesis is the division of the cell nucleus and separation of chromosomes while cytokinesis is the division of the cytoplasm and separation of other cellular components
Mendel's work with two-factor (dihybrid) crosses led directly to which law?
law of independent assortment
Mendel’s work with one factor monohybrid crosses led directly to what law?
law of segregation
complete dominance
for a given gene, the dominant allele completely masks the other allele
incomplete dominance
neither allele is completely dominant over the other, in which heterozygotes display a phenotypic blend
tay Sachs disease incomplete dominance example
homozygous recessive disease, but individuals who are heterozygous only have about half of normal enzyme function that of a normal individual (on a genotypic-molecular level)
over dominance (heterozygous advantage)
heterozygous genotype when viewing two different genes, has higher selective advantage/reproductive fitness
sickle cell disease overdominance example
Ss heterozygous individuals have an advantage against both non sickle cell, and being malaria resistant. While homozygous dominant are at a disadvantage having no malaria resistance, and homozygous recessive being full sickle cell disease
hybrid vigor (heterosis)
highly unrelated individuals mate, offspring will be heterozygous at most loci, often healthy and vigorous. ex: hybrid corn and mutts
inbreeding depression
two closely related individuals mate, many of same alleles, offspring are homozygous at many loci, often less vigorous, high incidence of recessive genetic disease
Co-Dominance
two dominant alleles, in which phenotypes are both expressed, neither of which are compromised.
Mechanisms to explain overdominance (3)
disease resistance, versatility in dimer formation (enzyme functional diversity), variation in functional activity
codominance example (ABO blood type)
blood types with a mix of genotype (ex: IA & IB), express both type A antigens and type B antigens, and neither are compromised
ABO blood types and antibody composition
depending on blood type, your body produces anti antigens for the blood type you do not have (note: type O can give their blood to anybody b/c they have no A or B antigens)
sex-linked inheritance
genes responsible for certain traits are located on sex chromosomes
hemizygous
in males, sex chromosomes are XY, and these chromosomes are very different from each other
ichthyosis sex linked inheritance example
impacts male skin, making it scaly, on X chromosome
reciprocal cross
in two crosses, first take a affected male and breed with a unaffected female, then, in the reciprocal cross, take a unaffected male and breed with a affected female. if ratios are different between crosses, it tells you the gene is X linked
X linked traits
can impact both males and females
Y linked traits
exclusively impact males
holandric genes
genes only found on Y chromosomes
SRY genes
found on Y chromosome in mammals, gene activation causes testosterone boost to signal male sex development
pseudoautosomal
fake autosomal inheritance so it looks autosomal, but truly is not
mic 2 gene example
of pseudoautosomal gene
sex influenced traits
trait influenced by what sex you are, commonly found in heterozygotes
example of sex influenced trait
scurs in cattle, Sc Sc = scurs in both sexes, but Sc sc = scuts in males only.
Sex limited trait
only seen in one sex & never in another (ex: physical appearance differences)
pleiotropy
one gene that is responsible/contributes to multiple different phenotypes
CFTR mutations are an example of
pleiotropy
epistasis
one gene can modify the effects of a completely different gene (multiple genes contributing to a common pathway)
epistasis example
phenotype of purple pigment is only expressed when complementation occurs in white pea plants
maternal effect genes
non mandelian inheritance pattern, only thing that influences phenotype of offspring is the genotype of the mother
null hypothesis
data observed are the result of random chance alone
chi squared formula
x^2 = (o-e)^2/e
Note 
Flashcard (36)