Genetics Exam 3
What always results from paracentric inversion?
1 dicentric gamete, 1 acentric gamete, 2 "normal" gametes
3 components of genetic variance (Vg)
1. Additive genetic variance (Va) additive alleles 2. Dominance genetic variance (Vd) effects of truly dominant v recessive alleles 3. Gene interaction variance (Vi) effects of genes from different loci interacting (epistasis) Vg= Va+ Vd+ Vi
How does recombination happen?
1. After replication, homologous chromosomes align and single-strand breaks occur in the same position on both DNA molecules 2. Free end of each broken strand invades/migrates into the other DNA molecule 3. invading strand is joined to the other DNA molecule, creating a holiday junction 4. Branch migration (away from centromere and orginal starting point) takes place, creating heteroduplex DNA eliminating holiday junction 5. ends of strands pull away from eachother 6. the interconnected DNA must be separated. Thus, the holiday junction must be cleaved 7. Vertical cleavage and rejoining of the stands produced crossover recombinants (repulsion created) 8. Horizontal cleavage and rejoining the strands produces non-crossover recombinants (coupling created)
Condensed version of recombination
1. DNA is replicated 2. homologous chromosomes align 3. breaks occur 4. broken end invades other DNA 5. invading end is joined to the other DNA molecule, creating holiday junction 6. branch migration 7. holliday junction is cleaved and strands are re-joined
3 components of phenotypic variance
1. Genetic variance (Vg) 2. Environmental variance (Ve) 3. Genetic-Environmental Variance (Vge) Vp= Vg+ Ve+ Vge
three consequences of meiosis
1. meiosis comprises 2 divisions, each original cell produces 4 cells 2. chromosome number is reduced by half= haploid cells 3. cells produced are genetically different
three key differences between mitosis and meiosis
1. mitosis consists of single nuclear division with single cell division 2. meiosis= two divisions 3. mitosis creates two genetically identical cells and meiosis creates genetically variable cells
three essential elements of a eukaryotic chromosome
1. origins for initiation of DNA replication 2. centromere 3. telomeres
Multiple alleles (3+) ratio
1:1:1:1 example ABO blood type
Assume that you are looking at a case of lethal alleles. Crossing two green corn plants results in 2/3 green progeny and 1/3 white progeny. If you crossed two green progeny with each other, how many of the progeny would you predict to be green?
2/3 of the progeny would be green in a green(Gg)xgreen(Gg) cross G= green g=white Gg= green gg= white GG= dead whenever ratios are in the thirds, you know you are dealing with lethal alleles
A diploid cell contains the chromosomes shown below (centromere as an "o"): wild-type: I: D E o F G H J K L M II: S o T U V W X Y Z translocation: I: D E o F G H W X Y Z II: S o T U V I J K L M How will these four chromosomes pair during meiosis I?
50% alternate segregation- viable normal-normal trans-trans 50% adjacent segregation- nonviable normal-trans normal-trans decreases fertility by 50%
Say that the broad-sense heritability of height among EMU students is 0.9. Which of the following conclusions is reasonable?
90% of the variation in height among EMU students is due to genetic variance H2= Vg/Vp H2=1=100% variation due to genetics
In a dihybrid cross, the phenotypic ratio will always be what?
9:3:3:1 9- dominant phenotype for both traits 3- dominant for phenotype A and recessive for B 3- dominant for phenotype B and recessive for A 1- recessive for both traits
Polyploid
A cell containing more than two homologous sets of chromosomes
Turner Syndrome
A chromosomal disorder in females in which either an X chromosome is missing, making the person XO instead of XX, or part of one X chromosome is deleted.
codominance
A condition in which neither of two alleles of a gene is dominant or recessive. A condition in which both alleles for a gene are fully expressed **generally seen at the genotypic (molecular) level
Karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
Triple X Syndrome
A genetic abnormality in which a female has an extra X sex chromosome; characterized by decreased fertility, some genital abnormality, and slight mental retardation.
Plasmid
A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome can replicate independently
simple regression analysis
A technique that allows us to describe a straight line that best fits a series of ordered pairs the more linear the line the closer it is to r
A woman who has blood type O and blood type MN marries a man who has blood type AB and blood type M. If we assume that the genes for the ABO and MN blood-typing systems assort independently, what blood types might the children of this couple have, and in what proportions?
ABO= only get two, AB codominant, O recessive MN= codominant, if you have one of each you express both, MM=M NN=N Women= iOiO MN dad= IAIB MM KIDS: mom gametes: 0.5 iO M ; 0.5 iON dad gametes: 0.5 IA M; 0.5 IB M; 0.5 IA M; 0.5 IB M CROSS 0.5 iO M (mom) x 0.5 IA M (dad)= 25% IAiO MM 0.5 iO M (mom) x 0.5 IB M (dad)= 25% IBiO MM 0.5 iO N (mom) x 0.5 IA M (dad)= 25% IAiO MN 0.5 iO N (mom) x 0.5 IB M (dad)= 25% IBiO MN
This is an X-linked dominant disease.D = disease d = normal. Write in the genotype of each individual in this pedigree.
Affected females= XDXd or XdXd (depending on offspring) Affected males= XDY normal females= XdXd normal males= XdY
autosomes
Any chromosome that is not a sex chromosome
How are archaea different from bacteria?
Archaea have different ribosomes Archaea found in extreme environments Eubacteria are found in everyday environments
what are the two types of prokaryotes?
Bacteria and Archaea
Dosage compensation (lyon hypothesis)
Cells only need one X chromosome to function Females have to do dosage compensation Inactivate one of their X chromosomes in each cell in their body (this is done randomly) Barr body= inactivated X chromosome Example of this effect= calico cats
continuous traits
Continuous traits are those that can exist in a range (height, age, skin color, etc.) skin color in humans
telomere
DNA at the tips of chromosomes protects the genome from degradation
An individual has the following homologous chromosomes, with genes labeled by letter and the centromere as an "o". A o B C D E A o B E What kind of mutation is present in the lower chromosome? how the chromosomes will look when paired up during meiosis I?
Deletion will form a deletion loop when paired up during Meiosis I
law of independent assortment
Each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random
Spermatogenesis
Formation of sperm production of gametes in male animal 2 haploid spermatids are produced from each spermocyte cycle
linked genes
Genes located on the same chromosome that tend to be inherited together in genetic crosses.
Meiosis I
Homologous chromosomes separate CELL XxXx (2n) --reduction division---> CELL 1 Xx (n) CELL 2 Xx (n)
What would this cell look like in metaphase 1?
IN SAME NUCLEUS big- XX XX medium- xx xx small- ii ii still has 6 chromosomes but they have been duplicated to homologous pairs. Each one individually is a chromatid and together a chromosome. ** could be arranged in any way as long as the same "sizes/types" go together
sister chromatids
Identical copies of a chromosome; full sets of these are created during the S subphase of interphase. both copies are joined together by centromere
Loci
Location of a gene on a chromosome
Mitosis VS Meiosis
MITOSIS preceded by replication of chromosomes one round of cell division two daughter cells same number of chromosomes in daughter cells (2n) daughter cells genetically identical to parent cell daughter cells genetically identical to each other NO synapsis of homologous chromosomes NO crossing over MEIOSIS preceded by replication of chromosomes two rounds of cell division four daughter cells Half number of chromosomes in daughter cells (1n) daughter cells genetically different from parent daughter cells genetically different to each other n synapsis of homologous chromosomes happens crossing over happens
Law of Segregation
Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
A child who is blood type A has a mother who is blood type B. In a paternity suit a man is accused of being the father. He has blood type AB. Is he the father?
Mom= BO Child=AO Dad=AB has to get A from dad he cannot be excluded as the father but it could be another person with type A blood
will everyone with a C allele of the rs1858830 develop autism?
No, they did notice that it was associated with and increased risk BUT the C allele isnt enough to cause autism on its own, when paired with specific environmental factors it will
incomplete penetrance
Not all individuals with a mutant genotype show the mutant phenotype the genotype does not always produce the expected phenotype
Basic structure of a virus
Nucleic acid core surrounded by capsid (protein coat)
Odds Ratio
OR=1 X does not affect the odds of outcome Y OR > 1= X associated with higher odds of outcome Y OR < 1= X associated with lower odds of outcome Y
The following progeny result from the F1 (BbNnxBbNn) that are testcrossed: black, normal 27 black, wavy 13 white, normal 16 white, wavy 24 Total= 80 Are these two genes are assorting independently? Test your hypothesis using a chi square analysis.
Observed= 27, 13, 16, 24 Expect: 20,20,20,20 Chi2= 2.45, 2.45, 0.8, 0.8 X2= 2.45+2.45+0.8+0.8= 6.5 DF= 4 categories-1= 3 our x2 is less than the value on the chart so we accept our null hypothesis the samples are not significantly different they are assorting independently
independent assortment
One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes
In Drosophila, body color is an X-lined gene. G = gray body g = yellow body A homozygous gray female is crossed with a yellow male. The F1's are crossed to produce F2. Give the genotypes, phenotypes, and proportions of the F2 offspring.
P mom= XGXG P dad= XgO F1 females= XGXg F1 males= XGO F2 generation= XGXG ; XGXg ; XgO ; XGO All females gray; 50% males gray; 50% males yellow
Two parents are AaBbCC and AABbCc.• What is the probability that they will have a child who is AABBCC?
Parent 1 gametes= ABC, AbC, abC Parent 2 gametes= ABC, AbC, Abc 50% A from P1 x 100% A from P2 = 0.5 x 1 = 0.5 or 50%50% B from P1 x 50% B from P2 = 0.5 x 0.5 = 0.25 or 25%100% C from P1 x 50% C from P2 = 1 x 0.5 = 0.5 or 50% 0.5 AA x 0.25 BB x 0.5 CC = 0.0625 or 6.25% chance of being AABBCC
Crossing over
Process in which homologous chromosomes exchange portions of their chromatids during meiosis. exchange of genetic material between nonsister chromatids; after this happens cells are no longer identical; same chromosomes new combinations
Phases of Meiosis
Prophase 1- chromosomes begin to condense and spindles form; homologous chromosomes pair; crossing over takes place and the nuclear membrane breaks down Metaphase 1- Homologous pairs of chromosomes line up along the metaphase plate Anaphase 1- Homologous chromosomes separate and move toward opposite poles Telophase 1- chromosomes arrive at the spindle poles CYTOKINESIS 1- cytoplasm divides Prophase 2- the chromosomes re-condense Metaphase 2- individual chromosomes line up at the equational plate Anaphase 2-sister chromatids separate and move toward opposite poles Telophase 2- chromosome arrives at the spindle poles CYTOKINESIS 2- cytoplasm divides
A woman has a rare abnormality of the eyelids called ptosis, which prevents her from opening her eyes completely. The condition is caused by a dominant negative allele, P. The woman's father had ptosis, but her mother had normal eyelids. •What are the genotypes of the woman, her father, and her mother? What proportion of the woman's children will have ptosis if she marries a man with normal eyelids?
Ptosis= PP or Pp the mother of the women= pp father= Pp or PP women= Pp (because her mom passed on a p) women and man with normal eyelids women=Pp man=pp 50% chance of her children having ptosis
centromere
Region of a chromosome where the two sister chromatids attach
what is rs1858830
SNP that is associated with the expression of the MET protein in the brain
incomplete dominance
Situation in which one allele is not completely dominant over another allele A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits. **seen at the phenotypic (zoomed out) level
Expressivity
The degree to which an individual carrying a particular genotype also expresses that gene Example: to what degree is someone polydactyly? do they have a complete extra digit, a nub, or a partial extra digit etc.
epistasis
The interaction of genes, in particular the suppression of the effect of one such gene by another Ex: mouse coat color
While examining a Calico cat, you and the veterinarian you are interning with get a surprise - the cat is male, not female! How can this be?
This is an XXY male cat. Nondisjuction caused XblackXorange on both alleles and a Y chromosome to make it male
An individual is heterozygous for an inversion as diagrammed below (centromeres represented by circles and genes represented by numbers): Normal: 1 2 O 3 4 5 6 Inverted: 1 4 3 O 2 5 6 What is the term for the type of inversion shown? Will this change have an impact on gene function?
This is pericentric inversion Position effect. Meiosis should be able to occur. The closer the gene is to a centromere, the more likely it is to be expressed
Blood type genotypes
Type A: IAIA/IAi Type B: IBIB/IBi Type AB: IAIB Type O: ii
A healthy student constructs a karyotype from a cell from the inside of her cheek. She finds only one chromosome 3 and one chromosome 21, plus two unusual chromosomes that do not seem to have any matching partners. What type of chromosomal abnormality does she have? Why doesn't she have any symptoms? Would you expect her to have any difficulty conceiving children?
What type of chromosomal abnormality does she have? Translocation- hybrids of chromosome 3 and 21 Why doesn't she have any symptoms? It's a reciprocal translocation, she has all of the genes just on different chromosomes Would you expect her to have any difficulty conceiving children? Yes, depending on how the abnormal chromosomes synapse
When do you double the DC in your distance calculations?
When you are calculating the two OUTSIDE genes
In humans, red-green color blindness is an X-linked recessive disorder. A man has Kleinfelter Syndrome (47, XXY) and is color blind. Both of his parents have normal color vision.How did this man inherit color blindness?
X-linked recessive= expressed on the X chromosome He had to have inherited it from his mom. Men are XY Women are XX Mom had to be X-normal X-colorblind Probably in meiosis II the colorblind gene underwent nondisjunction to create XXY (where both of the X's in the son had the recessive colorblind gene) *** this is an example of sex chromosome aneuploidy
chiasmata
X-shaped regions where crossing over occurred.
fruit fly sex determination
XX female XO mail
Can chromosomal duplications cause negative effects to an organism?
Yes. Duplicated regions increase gene dosage which can effect processes like development that require specific amounts of protein
Chicken sex determination
ZW female ZZ male
Diploid
a cell containing 2 complete sets of chromosomes, one from each parent
hapliod
a cell that contains one of each kind of chromosome. a single set of unpaired chromosomes
test cross
a cross between an individual with an unknown genotype and one with a homozygous recessive genotype. The outcome of the test cross can reveal the unknown genotype.
heterozygous
a diploid organism with a genotype consisting of two different alleles
homozygous
a diploid organism with a genotype consisting of two identical alleles
Giemsa stain
a process of staining bacteria for identification
MET
a receptor for tyrosine kinase gene receptor protein gets phosphorylated on tyrosine when its activated
complete dominance
a relationship in which one allele is completely dominant over another The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.
chromosomal duplication mutation
a segment of a chromosome is repeated AB CDEFG ABAB CDEFG
This is an X-linked recessive disease.D = normal d = disease. Write in the genotype of each individual in this pedigree.
affected females= XdXd affected males= XdY normal females= XDX? normal males= XDY
X homologous genes
allow X and Y to pair
gene
an inherited factor that determines a characteristic
autosomal dominant trait
appears in males and females (not sex-linked) does not skip generations every affected person has an affected parent
In humans, what is the connection between aneuploidy and maternal age?
as people age the rate of aneuploidy increases as people age our bodies tend to make more mistakes (mostly trisomy)
what percent of miscarriages have chromosome defects (aneuploidy)
at least 50%
what is the name of the process by which prokaryotic cells divide?
binary fission
Meristic traits
can be counted and expressed in whole numbers number of branches on a rose bush
Sertoli cells
cells found within the seminiferous tubules that provide metabolic support for the spermatids
aneuploidy
change in the number of individual chromosomes into an abnormal amount
threshold traits
characteristics that only have two phenotypes but their expression depends on multiple other factors presence or absence of leprosy
most human embryos with aneuploidy of an autosomal chromosome are miscarried. Which autosomal chromosomes can be aneuploid in humans?
chromosome 21 because these chromosomes are small and carry fewer genes so the presence of extra copies is less detrimental than if it is for larger chromosomes
genetic sex determination
chromosomes determine sex of offspring
polyploidy
condition in which an organism has extra sets of chromosomes 3n, 4n, 5n etc.
Additive alleles
contribute a set amount to phenotype aabbcc squash= 3 lbs every added allele adds 0.5 lbs AaBbCc= 4.5 lbs (3 added alleles)
discontinuous traits
controlled by variation in one gene (ex. All or nothing traits) number of fingers in humans, kernel corn in wheat, presence or absence of cystic fibrosis
coupling vs repulsion
coupling- dominant alleles together; recessive alleles together repulsion- one dominant and one recessive on each chromosome
monohybrid cross
crosses between parents that differ in a single characteristic
dihybrid cross
crosses between parents that differ in two characteristics
allele
different types of genes that encode different characteristics
A certain species has 6 chromosomes (2n=6) in the G1 stage of the cell cycle. Is this species diploid or haploid? Is it eukaryote or prokaryote?
diploid (2 big XX, 2 medium xx, 2 small ii) eukaryote (prokaryote do not have nucleus)
paracentric inversion
does not include centromere
synergistic interaction
effect is greater than the sum of their individual affects x alone=1 y alone= 1 x and y together= 3
additive interaction
effects equal the sum of each factors individual effect x alone= 1 y alone=1 x and y together=2
Androgen Receptor (AR)
gene is only on the X chromosome codes for protein that is a receptor for testosterone when it binds to testosterone, it goes into the nucleus, then binds DNA and turns other genes on ** if testes are present, the genes that are now "on" cause development of male sex characteristics ** if ovaries are present, AR needed to turn on genes for their fertility
In guinea pigs, black (B) is dominant to white (b), and normal hair (N) is dominant to wavy hair (n).A breeder crosses a guinea pig that is true breeding for white, wavy hair with a guinea pig that is true breeding black, normal hair. The F1 are then testcrossed. Write the genotypes of the two parent guinea pigs. Write the genotype of the F1.
genotypes for two parents= bbnn x BBNN F1= all BbNn
monohybrid cross ratios
genotypic= 1:2:1 phenotypic= 3:1
Mules result from a cross between a horse (2n=64) and a donkey (2n=62). •How many chromosomes does a mule have? •Mules are almost always sterile. Why?
horse haploid= 64/2= 32 donkey haploid= 62/2= 31 Mule has 32+31= 63 chromosomes Mules when they undergo gamete formation are either missing a chromosome or have and extra one because they have and odd number of chromosomes
A fruit fly has four pairs of chromosomes (2n = 8). A house fly has six pairs of chromosomes (2n = 12). In which species would you expect to see more genetic variation among the offspring? Explain.
housefly should have more genetic variation assuming they have the same crossover rate. Housefly has more chromosomes to undergo crossing over (more chances). Higher change for independent assortment.
Heritability
how much of the phenotypic variation is due to the differences in genetics vs due to the environmental differences
homogametic
human females XX will only pass on an X
herterogametic
human males XY can pass down either an X or Y
pericentric inversion
includes centromere
random separation of homologous chromosomes
independent assortment happens in anaphase 1; the different migrations produce different combinations of chromosomes in resulting cells; different chromosomes new combination
variable expressivity
individuals with the same genotype may have different phenotypes
chromatin
loose combination of DNA and proteins that is present during interphase 2 chromatids make up a single chromosome
chromosomal deletion mutation
mutation where part of the chromosome is lost; body structures may be missing AB CDEFG AB CDE
trisomy
n+1 when fertilized by normal sperm 3 copies of a chromosome
monosomy
n-1 when fertilized by normal sperm missing a chromosome
Prokaryotic cells
no nucleus, 0.1-0.5 um, no true chromosome plastids, circular DNA, smaller amount of DNA, no cell membrane or membrane bound organelles
what is the cause of all sex chromosome abnormalities?
nondisjunction
two highest numbers are
nonrecombinants/parentals (have to be compliments)
Non-disjunction in meiosis 1
normal meiotic division results in 4 haploid cells all 1n Non-disjunction in meiosis 1: 2 cells are n+1 and 2 cells are n-1 no way to get a normal fertility out of this
Non-disjunction in meiosis 2
normal meiotic division results in 4 haploid cells all 1n Non-disjunction in meiosis 2: one cell= n+1 one cell= n-1 two cells= 1n (normal) 50% fertility in this female
Eukaryotic cells
nucleus, 5-100 um, more than one number of chromosomes present, linear DNA, larger amount of DNA, has membrane and membrane bound organelles
dominant epistasis
only 1 allele must be inherited to mask the other 12:3:1 ratio
locus
place on chromosome where genes are found
The authors report over-transmission of the "C" allele at marker #3 (rs1858830) in autistic individuals. Where exactly is this SNP? promoter? intron? exon?
promotor suggests that this allele is expressed differently than the G allele
stages of mitosis
prophase, metaphase, anaphase, telophase G1- cells recovering from meiosis of mitosis S phase- DNA synthesized G2- cell makes sure synthesis is done before mitosis
narrow sense heritability
proportion of the phenotypic variance that can be attributed to additive genetic variance h2=Va/Vp
broad sense heritability
proportion of the phenotypic variance that can be attributed to genetic variance H2= Vg/Vp
chromosomal rearrangements
rearranging the individual parts of a single chromosome or a pair of chromosomes duplicates, deletions, inversions, translocations
autosomal recessive trait
seen in both males and females skips generations appears more often among related parents
chromosomal translocation mutation
segment of DNA from one chromosome is swapped with a segment from another chromosome AB CDEFG AB CDEXYZ
chromosomal inversion mutation
segment of DNA is reversed within the chromosome AB CDEFG AB CFEDG
origin of replication
sequence of DNA at which replication is initiated
genotype
set of alleles that an individual organism posesses
SNP
single nucleotide polymorphism a single nucleotide difference in a sequence often in DNA between genes (otherwise there are mutations) occur once every 300 nucleotides on average Used to identify genes that are linked to quantitative characteristics
Meiosis II
sister chromatids separate CELL 1 Xx (n) ---equational division--> CELL 1 Ii (n) CELL 2 Ii CELL 2 Xx (n)---equational division--> CELL 1 Ii (n) CELL 2 Ii end with 4 genetically different cells
polar body
small haploid cell that is formed as an egg cell during oogenesis
pseudoautosomal region
small region on the X and Y chromosomes that contains homologous gene sequences
is the interaction between MET rs1858830 genotype and traffic air pollution synergistic or additive? Explain.
synergistic because by itself genotype has no linkage to autism but when you add in the air pollution the OR jumps drastically genotype alone= 0.9 pollution alone= 1.7 genotype and pollution= 2.7
phenotypic variance
the amount of phenotypic variance in a population Vp
If a color-blind female has children, what do we know about all of her sons?
the color blind gene is a X sex chromosome trait All of her sons will be color blind mom= X colorblind X colorblind Dad= XY All sons will get the colorblind allele from the mom because the Y will come from the dad
two lowest numbers are
the double crossovers (have to be compliments)
Non-disjunction
the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei. Aneuploidy can arise from this
Genetic distance
the greater the distance between two linked genes, the greater the chance of a crossover between the genes. Hence, the greater the distance between the two linked genes, the greater the frequency of recombinants produced Genetic distance is defined as centiMorgan (cM)
phenotype
the manifestation/appearance of a characteristic
F2 generation
the offspring of the F1 generation
F1 generation
the offspring of the parents in the P generation
penetrance
the percent of individuals carrying a particular allele of a gene (genotype) that also express an associated trait (phenotype) Example: % of individuals with the dominant polydactyly gene that actually show polydactyly
oogenesis
the production, growth, and maturation of an egg, or ovum the production of gametes in a female animal produces a single mature gamete from each primary oocyte
SRY gene
the sex determining region of the Y chromosome in males. Encodes the testis-determining factor, which turns the primordial gonads into the testes
Say that the sperm from a particular species have 4 chromosomes. What is true about these chromosomes
there are 8 chromosomes in the primary spermatocyte during telophase II of meiosis, the spermatocyte cells have 4 chromosomes, each composed of a single chromatid
A diploid cell contains the chromosomes shown below: wild type: D E o F G H I J K L M inversion: D E o F G J I H K L M How will these chromosomes pair during meiosis? What four gametes will form from meiosis if there is no crossover event between j and k?
this is a paracentric inversion they will make an inversion loop **creates dicentric bridge Gametes: 1 dicentric (nonviable) 1 acentric (nonviable) 2 normal (one with inversion one without; both viable) 50% fertility at best
what are the most common aneuploidies in living humans?
those that involve sex chromosomes
polygenic trait
trait that is produced by two or more genes
dominant
traits that appear unchanged in the F1 heterozygous generation
recessive
traits that disappeared in the F1 heterozygous generation
recessive epistasis
two alleles must be inherited to mask the other 9:4:3 ratio
homologous pair of chromosomes
two chromosomes that have the same kinds of genes (alleles) in the same order A set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization
Genome Wide Association Studies (GWAS)
used in association to search the genome for SNPs that occur more frequently in people with a particular disease or trait since you are looking at the WHOLE genome, this is useful for looking at polygenic, complex disease data represented using a Manhattan plot
multifactorial trait
variation in traits caused by genetic and environmental or lifestyle factors
Weight of humans in city #1 has a narrow-sense heritability value of 0.9. Weight of humans in city #2 also has a narrow-sense heritability value of 0.9. Weight of humans in city #1 has a narrow-sense heritability value of 0.9. Weight of humans in city #2 also has a narrow-sense heritability value of 0.9. Can we conclude that the difference in weight of humans between these two cities is due to genetic differences between the two populations? Explain.
we can conclude that the variation is due to genetics, BUT we cannot say the trait is determined strictly by genes. Heritability tells us what causes variation NOT what genes control the development of a trait
In humans, SRY is located near a region of homology between the X and Y chromosomes that allows them to synapse during meiosis. About 1/25,000 newborn infants is born with sex reversal; either the infant is has a male phenotype and is XX, or the infant has a female phenotype and is XY. Propose an explanation.
when synapse occurs between X and Y chromosomes the homologous regions can swap. The SRY gene could go with. Could have and X chromosome with the SRY gene (nondisjunction)
