Bio: Genetics and Evolution Flashcards
Griffith Experiment
Two strains of bacteria -> S (smooth) and R (rough)
S was virulent so killed mice, R didn’t
When heat killed S was added to R, the mouse died so they knew the cell extract of dead S was capable of conferring virulence to R strain
Avery-MacLeod-McCarthy Experiment
Took the S strain extract from Griffith Experiment and see if mouse died if destroyed virus’ RNA, lipids, Polysaccharides, protein and DNA
When DNA destroyed mouse survived
This suggested that DNA was able to transform bacteria, and was the molecule of heritability that scientists has been looking for
Hersey-Chase
Phage T2 was added to E. Coli in either radioactively labeled 32P or 35S
So ultimately the capsids of the 35S radioactive phages were labeled and the genome of the 32P phages were labeled
Then they allowed phages to infect bacteria and only the bacteria that were infected by 32P phages demonstrated genetic material with 32P -> Supports that DNA carries genetic information in the cell
Diploid
Have two copies of genetic material in cell -> one from mom and one from dad
Main similarities and differences between mitosis and meiosis? Product of each?
Sim -> both have replication of genome before (S phase) to make sister chromatids
Diff -> mitosis: one round of cell division, meiosis: 2 rounds of cell division (meiosis I and II), recombination b/w homologous chromosomes
Another diff = meiosis is terminal process, once you do it once you’re done
Mitosis product: 2 identical diploid autosomes
Meiosis: 4 haploid gametes
Names steps of meiosis, describe process of prophase: (mention if haploid)
Bivalent
Tetrad
Prophase, metaphase, anaphase, telophase
Begin as diploid (like mitosis)
Prophase: longest phase, like mitosis, chromosomes condense, nuclear envelope breaks down.
Unlike mitosis, **homologous chromosomes pair during prophase I in synapsis with two copies of each gene on two different chromosomes brought closely together. The paired homologous chromosomes are called bivalent tetrad, genes can then be swapped by crossing over
Synaptonemal complex (SC)
Synapsis is mediated by Synaptonemal complex (SC) which holds the chromosomes together, there is more specifics page 233
Describe metaphase I
Independent assortment
Describe anaphase I
Telophase I (are the cells haploid or diploid?)
Then what happens/how does it relate to mitosis (sim and diff)? What do you get at the end?
Metaphase I:
alignment along metaphase plate, as in mitosis
Independent assortment = how homologous chromosomes line up
The difference: in mitosis sister chromatids lined up at plate but in meiosis tetrads are aligned at plate
Anaphase I: homologous chromosomes separate and sister chromatids remain together
Telophase I: the cell divides into into two cells, these cells are considered haploid, each cell has a single set of chromosomes and each chromosome is pair of sister chromatids, then cytokinesis
Then meiosis II begins and the movements of chromosomes are identical to those of mitosis with the sole difference being that in meiosis II there is haploid number of chromosomes, while in mitosis there is diploid number.
The sister chromatids are separated during anaphase II and after telophase II, you get four haploid cells produced from single diploid parent cell
each cell 1n1x
Are the sister chromatids that separated during meiotic anaphase II identical in their DNA sequence?
No -> recombination
True or false:
In meiosis recombination occurs between sister chromatids
Gametes normally contain how many copies of each chromosome?
What does recombination allow for?
FALSE
recombination occurs in meiosis only between homologous chromosomes
Gametes normally have one copy of each chromosome = haploid
Recombinaton produces new combinations
of alleles not found in parent and allow allows genes located on the same chromosome to assort independently
Nondisjunction during meiosis I and II:
What do the gametes look like with nondisjunction during meiosis I and of one of the cells in meiosis II?
Nondisjunction during meiosis I = 2 gametes with no copies of chromosome and 2 gametes with 2 copies of chromosomes
Nondisjunction of one of the cells during during meiosis II = 2 normal gametes, 1 with no copies of chromosomes, 1 with 2 copies
What can nondisjunction lead to?
Trisomy bc one of the bad gametes may have extra chromosome and fuse with normal one -> can get trisomy
or can fuse with gamete with no chromosomes and get monosomy (one chromosome)
What is Mendel’s law of segregation, when does it occur?
What is independent assortment, when does it occur?
Law of segregation -> two alleles of an individual are separated and passed on to the next generation singly
anaphase I and anaphase II
Law of independent assortment -> How one pair of alleles separate is independent of how other pairs separate - prob bc line up in different ways (alleles of one gene will separate into gametes independently of alleles for another gene)
metaphase I
True-breeding/pure-bred
testcross
= homozygous (identical alleles)
an organism that always passes down certain phenotypic traits (i.e. physically expressed traits) to its offspring of many generations
When a strain always produces the same trait when mated with itself, it is likely to be homozygous for the trait
ex. True breeding green plant GG
true breeding yellow plant gg
testcross -> cross something with homozygous (true-breeding) recessive genotype to determine its genotype
Incomplete Dominance
If the phenotype of a heterozygote is a blended is blended mix of both alleles
red flower and white flower make pink flower
Codominance
What is the main example and its alleles?
Two alleles are both expressed but are not blended. For example, the alleles of ABO blood group antigens that are found on the surface of red blood cells display codominance
IA, IB, i
IA and IB are codominant and will be expressed regardless of the second allele, while i is recessive to both IA and IB
There is also other main antigen in blood typing called rhesus = Rh
RhDRhD (also seen as RR) -> positive
RhdRhd (also seen as rr) -> negative
can also be heterozygous
Codominance
What is the main example and its alleles?
Two alleles are both expressed but are not blended. For example, the alleles of ABO blood group antigens that are found on the surface of red blood cells display codominance
IA, IB, i
IA and IB are codominant and will be expressed regardless of the second allele, while i is recessive to both IA and IB
There is also other main antigen in blood typing called rhesus = Rh
RhDRhD (also seen as RR) -> positive
RhdRhd (also seen as rr) -> negative
can also be heterozygous
For Rh factor only, you have to be exposed to Rh first before make antibodies to it (unlike for blood type ex. b) but eventually anti-Rh AB form so this bad blood donation is not a horrible but if happens again, the recipient already have anti-Rh ab ready to attack and this is BAD
Rh + , Rh -
ex. hemolytic newborn: second baby if Rh+ the mom’s anti-Rh+ ab’s (If she is Rh-) can cross placental barrier (unlike anti-A, anti-B, etc bc too big to cross) and attack bc her body has already seen Rh+ before
Pleiotropism
A gene that affects several traits ex. sickle cell
gene has pleiotropic effects if its expression alters many different, seemlingly unrelated aspects of the organism’s total phenotype. For example, a mutation in a gene may cause altered development of heart, bone, and inner ears.
Polygenism
Trait that is determined by several genes ex. height
Complex traits that are influenced by many genes. These traits tend to display a range of phenotypes in a continuous distribution.
For example height is polygenic and is influenced by genes for growth factors, receptors, hormones, bone disposition, muscle development, E utilization, and so on. As a consequence there is a wide range of heights
Epistasis
Expression of alleles for one gene is dependent on a different gene -> for example, a gene for curly hair cannot be expressed if a different gene causes baldness