BIS 101 - Genetics Midterm 1--
What is an allele?
A variant of a gene
What is a null allele?
allele with a complete loss of gene function (ex: no product or product is not functional)
Gene is named after _______ phenotype
MUTANT -For Fruit Fly eye color: the red is the wildtype and the white is the mutant; therefore the gene is w for white-eye and w+ for red (wildtype) -Wildtype is not always dominant
How do geneticists study genes?
MUTANTS!
Why is mitosis important?
-Growth -Repair -Replacement -Cancer (result of uncontrolled cell division)
The dominant and recessive relationship is meaningful when comparing two alleles ........
relative to each other
Chromosomes are often visualized in their _____________
replicated form
What is the nondisjunction in Meiosis II?
-SIster chromatids fail to separate -Metaphase II and Anaphase II (specifically) -Result: n, n, n+1, n-1 ; therefore, it can result in normal gametes
Clicker Question: Experiments where researchers knock out a specific target gene in a model organism and analyze the resulting phenotype to get clues regarding the function of the target gene is an example of
reverse genetics
For linked genes, crossing over gives.......
rise to recombinant (non-parental) genotypes and phenotypes
During M phase, ___________ is/are attached to the spindle apparatus at the _________________
sister chromatids; Centromere
What were the results in Mendel's Crosses in which the Parents differed in 1 character?
~ 3:1 ratio
Describe Interference
A crossover in one region reduces likelihood of another crossover occurring nearby - I = 1 - C.O.C (Coefficient of coincidence) - 1 - (# of observed DCO)/(# of expected DCO) - I = 0 (no interference) - I > 0 (interference)
In the human Karyotype, how many genes?
Approximately 20,000 genes = roughly 1,000 genes/chromosome
What is a somatic cell?
Body cell (not gamete - egg/sperm)
Define the Law of Segregation in terms of meiosis
During meiosis, the alleles for each gene segregate away from each other so that each gamete carries only one allele for each gene -So mendel's law is saying that each parent starts with 2 alleles and by way of meiosis, each gamete gets 1 copy. Through fertilization, we are going to restore the offspring or 2n
Why are humans not good study subjects?
-Environmental differences -Slow reproduction -Small # of progeny -Cannot force matings between individuals of desired phenotypes
When you cross a fully functional genotype (black feather) with a null allele (white feather), what are the results?
1:2:1 -1 black, 2 GREY, 1 white
Assume that eye color is controlled by a single gene (not true), but assume it is, how many copies of that eye color gene would we have in a single human somatic cell?
2 -Humans are diploid (2 copies of each gene) -Therefore, one from mom and one from dad
What is Genetic Linkage and define the types?
2 genes are on the same chromosome in some what close proximity -Linked: genes are inherited as though on same chromosome -Unlinked: genes inherited as though on different chromosomes
What is the structure of chromosomes?
An unreplicated chromosome is composed of one double strand of DNA (one "double helix") wrapped around proteins -Unreplicated chromosomes are loosely coiled -Once replicated in prophase of mitosis or meiosis, chromosomes CONDENSE into more tightly coiled structures
You've isolated a mutant defective in meiosis that displays unpaired homologous chromosomes in meiosis I. for the mutant, what do you predict the wild type gene encodes? a.)A protein required for kineteochore formation b.)a protein that is part of the synaptonemal complex (SC) c.)a protein that is part of sister chromatid cohesion (SCC) d.)a protein required for DNA replication e.)all of the above
B
Define the Law of Independent assortment in terms of meiosis
Different gene pairs assort independently into gametes during meiosis -configuration of homolog pairs in Meiosis I is the basis of independent assortment. Just as likely that t lines with R as T lines with R (equally likely)
Mutant alleles of different genes =
F1 is WT --> complement
Mutant alleles of same gene =
F1 is mutant --> FAIL to complement
What is the recombination frequency?
Percentage of observed recombination events in the progeny -Rf = (total # of recombinants)/(total # of progeny)
What was Mendel's Model system?
Pisum sativum (garden pea) -Easy to grow -Easy to breed/cross -Easily observed traits -Self-fertilize & cross fertilization
Define Ploidy
The number of chromosomes in the nucleus of a cell
How do we get from Genotype to Phenotype?
Through the process of transcription and translation
What is haplo insufficient?
gene requires 2 fully functional alleles to produce the full function (WT) phenotype
What is the difference between the l shaped chromosome and the H shaped chromosome?
l shaped: -unreplicated (unduplicated) -homologous chromosomes = not exact copies & alleles inherited from parents differ -before S phase -after anaphase H shaped: -replicated (duplicated) = exact copies -after S phase -has sister chromatids
What is the df in chi squared tests equal to?
n-1
What is recessive lethal allele?
two copies of the alleles leads to lethality (death) -with a dead phenotype observed, this will change proportions because you will leave dead one out
In a single somatic cell within a diploid organism, there can be up to ______ of a given single-copy gene?
two different alleles
Rf is determined by
three point test cross (trihybrid cross = heterozygous for 3 genes)
Describe Forward Genetics
"Classical Genetics" -Phenotype --> Genotype -Start NOT knowing what the gene is -Mutate --> start with a phenotype --> identify the genotype (gene) -You begin with a mutant phenotype; you can infer function of the wild-type gene based on the phenotype; you can then use the mutant to identify the gene and analyze it on a molecular level
Define Diploid
(2n) -TWO copies of each chromosome
Genotype vs. Phenotype
-Genotype: composition of a set of alleles that an individual or cell carries -Phenotype: Physical manifestation of a genotype
What helps us visualize modes of inheritance?
Pedigrees
Describe Reverse Genetics
"Newer approach" -Genotype --> Phenotype -Start knowing what the gene is but not the specific function or phenotype -Know the gene --> mutate --> study the phenotype -Start w/ gene and make a mutant
What is a hypomorph?
(leaky alleles) -alleles that produce some degree of gene function -Ex: cherry, coral, apricot, and buff are hypomorphic alleles of white gene
Define Haploid
(n) -ONE copy of each chromosome
Describe the Fruit Fly
-Drosophila Melanogaster -Wild Type means the most common variant -Wild Type has Red Eye -Sexually Dimorphic (condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs)
What is Mendel's first law?
-1st Law of inheritance -"Law of Segregation" -Each parent has 2 characters (alleles of genes), each gamete (egg/sperm) gets alleles *When gametes combine, offspring have 2 alleles; 1 from each parent*
How many chromosomes total do humans have?
-46 total -Every cell has 2 copies of each of the 23 chromosomes
What is a gene expression?
-A particular gene turning on -Production of an end product driven by information encoded by DNA
Explain why the Central Dogma is not so Dogmatic (a principle or set of principles laid down by an authority)
-DNA does not need to go to RNA and then Protein -DNA can go to ncRNA (non-coding RNA; that does not code for a protein but still affects steps in the central dogma)
What was the purpose to know behind Mendel's Seven Characters (traits)?
-Discontinuous traits (no blends; either _ or _ ) -Unlinked genes (on different chromosomes)
Describe Autosomal Dominant
-Affected children have at least one affected parent -Does not skip generations -Equal number of affected males and females -Except for the rare cases of a new mutation, unaffected parents DO NOT produce affected children
Describe Autosomal Recessive
-Affected children often from unaffected parents -Mating between two heterozygotes has 1/4 chance of child being affected -Equal number of affected males and females -SKIPS generations -For RARE allels; matings between affected and unaffected individuals expected to result in unaffected children
What are the five modes of inheritance and what makes one unique?
-Autosomal recessive -Autosomal dominant -X-linked recessive -X-linked dominant -Y-chromosome (not recessive or dominant because 1 chromosome)
what are Common ways of representing a chromosomes?
-Blob containing centromere -Straight line containing centromere -Note: Genes that are contained in the chromosomes are represented by letters
What is the note about mutant genes when they are dominant?(example given)
-Capitalize Mutant that is dominant -Fruit Fly: Curly gene mutation is dominant over the wildtype; therefore, gene is Cy for curly wings (mutant) and cy+ for flat wings
What is a test cross?
-Cross to homozygous recessive -So either a RR x rr or Rr x rr -RR x rr : phenotypic ratio: all round ; genotypic ratio: all heterozygous -Rr x rr : phenotypic ratio: 1/2 round & 1/2 wrinkled ; genotypic ratio: 1/2 heterozygous & 1/2 homozygous
Describe crossing over between homologs
-Crossing over between homologs REQUIRED for Metaphase I chromosome segregation -Crossing over leads to exchange BETWEEN HOMOLOGS and generates NEW combination of alleles
What is the meiotic nondisjunction: Trisomy 21?
-Downsyndrome -3 copies of chromosome 21
Who is Gregor Mendel?
-Father of genetics -First to discover what genes are -Figured out patterns of inheritance
Describe the Central Dogma
-Gene expression is producing the end product of a gene -DNA --> RNA (via transcription) -RNA --> Ribosome (protein) (via translation)
Are genes sex-linked? (Major things to look for)
-Gene segregates differently in F1 generation of reciprocal crosses -Difference in inheritance between male and female progeny in F2
What are the components of sex determination?
-Genetic -Environmental (fish can be male/female based on the temperature of the water)
Define monohybrid
-Heterozygous for 1 gene (trait)
Define dihybrid
-Heterozygous for 2 genes (traits) -HUGE punnet square of RRYY x rryy giving Rr Yy and having to use FOIL
Define true breeding
-Homozygous for genotype/phenotype -For an individual to be true breeding it must be homozygous for both traits (i.e. rrYY, rryy, RRYY, or RRyy)
Homozygous vs. Heterozygous
-Homozygous: AA, aa (same alleles) -Heterozygous: Aa, aA (different alleles)
Give the Rf is genes are linked or unlinked
-If genes are LINKED; Rf < 50% (% rec. progeny) -If genes are UNLINKED; Rf > 50%
What is Mendel's 2nd Law?
-Law of independent assortment -Alleles of 2 different genes segregate independently of each other into progeny/gametes -Ex: dihybrid cross
Linked genes vs Unlinked genes
-Linked genes: genes on same chromosomes -Unlinked genes: genes on different chromosomes
Regarding Autosomal recessive, what is consanguineous mating?
-Mating between two family members of the same pedigree -results in a higher probability of producing affected offspring
What occurs after Prophase of Meiosis?
-Metaphase I: homologous chromosomes align opposite of each other at metaphase plate -Anaphase I of meiosis: homologous chromosomes segregate away from each other -Metaphase II of Meiosis II: chromosomes align at the metaphase plate -Anaphase II: sister chromatids align and segregate away from other -FOUR HAPLOID GAMETES produced
What is Mitochondrial Inheritance?
-Mitochondria have their own DNA: small circle of DNA with 37 genes -These genes function in energy production and protein assembly -Mitochondria are inherited only from the MOTHER (egg) - sperm contributes no cytoplasm to egg **all children are affected from affected mother; Children from affected father are unaffected**
Which is faster Mitosis or Meiosis?
-Mitosis because Meiosis has two rounds of division
What is the saying for mitosis and meiosis?
-Mitosis happens in your toes (somatic (body) cells) -Meiosis happens in your..... OH's!! (sex cells)
Difference between Monogenic Traits and Multifactorial Traits
-Monogenic Traits: traits controlled by a single gene -Multifactorial Traits: traits controlled by multiple genes and the environment
Describe X-Linked Recessive
-More affected males than females -All sons of affected females will be affected -Skips generations
What is the sum rule?
-One event, multiple outcomes are possible (two events are dependent) -Add probabilities together -Roll a 4 or a 5 on the dice = 1/6 + 1/6 = 2/6 *Observe dominant phenotype in offspring (genotype Aa or AA)*
What is the product rule?
-Probability of multiple independent events occurring together -Multiply probability of each event -Rolling a 4 on a dice and rolling another 4 = 1/6 * 1/6 = 1/36 *Probability of egg and sperm coming together*
After you cross F1 siblings, the result will be the parent progeny; what else will show?
-Recombination/crossover -Recombinants = new linkage of alleles
Reciprocal Crosses give different results! Give F2 for Red Female x White Male & White Female x Red Male
-Red Female x White Male: 3:1 ratio; Females: all red; Males: 1/2 red and 1/2 white -White Female x Red Male: 1:1 ratio; Females: 1/2 red and 1/2 white; Males: 1/2 red and 1/2 white
After DNA replication, what happens in Meiosis?
-SCC is present -Synaptonemal Complex present: allows for homologous chromosomes to come together to allow for crossovers to happen -Meiotic Prophase follows: homologous chromosomes pair and crossover
Describe Meiosis in the heterogametic sex (XY)
-Sex chromosomes behave as "pseudo" homologs -This allows X & Y to pair as if they were homologs -Maleness gene SRY & Pseudoautosomal region
How to distinguish between the 23 chromosomes?
-Size -Striped/banding pattern with lighter/darker staining regions
who is Dr. Nettie Stevens?
-Studied meal worms -Helped characterize sex determination -Helped establish that chromosomes were the genetic information that was heritable (Chromosome Theory of Inheritance)
What are the specific features of Meiosis I?
-Synapsis: pairing of homologous chromosomes -Crossover: physical linkages between homologs
Describe Modes of Inheritance
-Tells us how traits are passed between generations -Knowing the mode of inheritance can help us predict the chances that an individual will have a disease or be a carrier of a particular allele
What are conditional alleles?
-The Ch allele in cats -The Ch allele produces dark pigment (Temperature sensitive alleles) -At warm temperatures (the cat's body), the protein is inactive (Restrictive Temperatures) -At cooler temperatures (the cat's extremities), the protein is active (Permissive Temperatures) **Protein Product is made at both warm and cool temperature**
What is genetics?
-The study of genes Genomics = the study of all of the genes that make up an organism
Given: P: white x agouti F1: agouti P: snow x agouti F1: agouti P: blanca x agouti F1: agouti what can we infer?
-The white, blanca, and snow mutant alleles are recessive to wildtype **just because you have mutations that lead to the same phenotype does not mean that all mutations are within the same gene itself**
Other than Dr. Nettie Stevens, who were the founding fathers of the Chromosome theory of Inheritance?
-Thomas Hunt Morgan -Calvin Bridges
Describe Y-Linked inheritance
-Traits on the Y chromosome are only found in males; therefore, never found in females -The father's traits are passed to ALL SONS -Dominance is irrelevant; there is only 1 copy of each Y-linked gene
Describe X-Linked Dominant
-Twice as many females as males affected -All daughters of an affected male are affected -Does not skip generations
What is Turners Syndrome?
-XO -1 X and no Y
What is Klinefelter's Syndrome?
-XXY -2 X and 1 Y
What is the Chi-square test?
-a goodness of fit test -determine if the deviations in your data are caused by sampling/experimental error, or a real difference -Start with null hypothesis that data is not different than expected (Ho) **Want to reject the null hypothesis**
Conclusion from reciprocal cross?
-genetic material is NOT equal/identical between the sexes **the w+ gene is on X-chromosome in drosophila. "X-linked"**
What is the nondisjunction in Meiosis I?
-homolog pair fail to segregate away from each other -Occurs during Metaphase I and Anaphase I (specifically): homologous chromosomes do NOT segregate away from each other -Result: all gametes have either an extra chromosome (n+1) or are missing a chromosome (n-1)
Why is meiosis important?
-sexual reproduction -reducing ploidy -genetic diversity
What is Mitosis?
-somatic (body) cell division -2n into 2n & 2n (two identical cells)
Describe the Mitosis cycle
1.)Ex: Chr 1 has A from mom and a from dad; Chr 3 has B from mom and b from dad 2.)DNA replication: two identical copies are formed; therefore now there is a A with an A (sister chromatids). Held together by Sister Chromatid Cohesion (SCC) 3.)Metaphase of Mitosis: sister chromatids align opposite of each other along metaphase plate 4.)Anaphase: sister chromatids separate and segregate into opposite sides of dividing cell 5.)Cell divides (cytokinesis); 2n has split into two identical copies of 2n
What are the steps for calculating Probability?
1.)Gather info and assign mode of inheritance 2.)Assign known genotypes in pedigree 3.)Assign unknown (possibile) genotypes and their probabilities 4.)Calculate final probability of given genotype or outcome
What are the steps are meiosis? (Simple)
1.)DNA replication 2.)2 rounds of chromosome segregation
What are the steps to Recombination Mapping?
1.)Define the parental cross (most frequent progeny): determine allele configuration (cis/trans) of trihybrid parent 2.)Define double cross over (DCO) class (least frequent progeny) 3.)Determine gene order by comparing allele configuration between parental homologs and DCO's: gene that switched relative to the other two is gene in the middle 4.)Calculate Rf between the first & middle, then middle & last. Divide by total # of progeny
What are the three notes about Linkage and Recombination?
1.)During Meiosis, linked alleles do not always assort together 2.)Parental phenotype combination (genotype) is more common in progeny than recombinant phenotype combination (genotype) 3.)Recombinant progeny are produced by crossing over in meiosis - physical breakage and union of homologous chromosomes in meiosis (crossing over)
What is a gene?
A sequence of DNA that encodes information that results in a functional biological end product (can actually be protein or RNA) -basic unit of biological function -implies a specific location
After Thomas Hunt Morgan and Calvin Bridges, in 1932 who took over the Genetic Linkage and Mapping?
Barbara McClintock and Harriet Creighton
Which of the following statements are true? a.)Chromosome segregation patterns in mitosis are the basis for Mendel's law of segregation b.)Chromosome segregation patterns in mitosis are the basis for Mendel's law of independent assortment c.)Mitosis generates two daughter somatic cells that are genetically identical to the parent d.)In mitosis, homologous chromosomes segregate away from one another e.)All of the above
C -A and B would be right if it was MEIOSIS, not MITOSIS
Where do the cross over events occur?
Chiasmata
what is unique about Chr 9?
Chr 9 has a knob
What are the different allele configurations? (and describe)
Cis: -Both WT or mutant alleles are on same homolog Trans: -WT or mutant alleles are on OPPOSITE homologs
What is the Complementation test?
Cross 2 true-breeding recessive mutants with the same phenotype to determine if mutations are in different genes or if they are mutant alleles of same gene **used when mutant is recessive to wildtype**
Explain Morgan & Bridges reciprocal cross (in true-breeding lines) for Red eye (male) w+/w+ x White eye (female) w/w
F1: all female red eyes and all males white eyes *Observation: F1 generation of reciprocal crosses are different! Difference in segregation of trait in female and male* GENE IS SEX-LINKED *Cross F1 siblings: w+/w+ (female) x w/w (male)* F2: Females are 1/2 white and 1/2 red; Males are 1/2 white and 1/2 red
Explain Morgan & Bridges reciprocal cross (in true-breeding lines) for Red eye (female) w+/w+ x White eye (male) w/w
F1: all red eyes (female and male): w+/w **cross F1 siblings: w+/w(female) x w+/w(male)** F2: All female have red-eyes; males have 1/2 white and 1/2 red -Differences in segregation of trait between female and male progeny
True/False Mendel's 2nd Law, that characters (genes) of a trait segregate independently of each other, is always true
FALSE -if genes are on same chromosomes, that is not true -They will segregate together (they are linked)
True/False: All traits will segregate the same regardless of whether they are inherited from the maternal or paternal parent
FALSE; because of the Y chromosome and the linkage that we see
What is the Eukaryotic Cell Cycle?
G1 (Gap phase/Growth Phase), S (DNA synthesis), G2, and M (Cell division or mitosis)
What is haplo sufficient?
Gene where 1 fully functional allele is enough to produce the fully functional (WT) phenotype
Most phenotypes are influences by ____ and _____
Genes and the environment
What is recombination frequency (Rf) directly proportional to?
Genetic Distance -Map units (mu) -Centimorgan (cM)
What is incomplete dominance?
Heterozygotes show an intermediate phenotype between either homozygote --> between fully functional and null phenotypes -Incomplete dominance is a dosage dependency on the amount of gene product (Neither allele is dominant)
What is Co-dominance?
Heterozygotes show the phenotype of both alleles equally -ex: IA IA = blood type A; IB IB = blood type B; therefore, IA IB = blood type AB
What Sister Chromatid Cohesion? (SCC)
Holds sister chromatids together (kinda like glue) -In mitosis and meiosis
Which way does the p-value go in order to Accept and reject the null hypothesis?
If p-value (0.05): -Goes left (toward bigger numbers): accept the null hypothesis -Goes right (toward smaller numbers): reject the null hypothesis
What is the determination of sex for Mammals vs Fruit Flies?
In mammals: Presence of the Y chromosome determines Sex (XX: female; XY: male; XXY: male; XO: female) In Fruit Flies: # of X chromosomes determines Sex: Greater than or equal to 2 is Female and less than 2 is male (XX: female; XY: male; XXY: female; XO: male)
Define Crossing over
In meiosis I, when homologs pairs and crossover, they can exchange corresponding chromosome parts by breakage and reunion
Null Hypothesis and linked/unlinked genes?
In the null hypothesis, genes are unlinked! (25% of each; 1:1:1:1 ratio)
What is the background of Pedigree analysis?
Law of Independent Assortment (Mendel's 2nd Law)
Quick Note: Linked Alleles tend to be inherited together; therefore....
Linked alleles do not follow Mendel's Law of Independent Assortment
Law of independent assortment does NOT apply to....?
Linked genes
In a population, there can be _________ allele(s) of a given single-copy nuclear gene.
MANY -each individual will only have 2 copies (since we are diploid) but there could be lots of different versions
Define complex trait
Many genes --> one phenotype
What does the O in XO mean? (chromosomes)
Means no 2nd sex chromosome
At what stage in Meiosis does the chromosome change from diploid to haploid?
Meiosis Metaphase I
What is the note about mtDNA mutations?
Mitochondrial DNA mutations cause human diseases
Instead of using humans for study subjects, we use ______
Model organisms (E coli, etc) -Genetically homogenous (vs humans) -Can be propagated under controlled environmental conditions -Fast reproduction and produce loss of offspring -Short life span
What are allele interactions?
Multiple alleles of given gene nature how alleles interact
Not all DNA......
Not all DNA encodes for genes
Define a simple trait
One gene ---> One Phenotype
Define Pleiotropy
One gene ---> many phenotypes
Parental vs Recombinant
Parental: -chromosome allele configuration of linked alleles is identical to what parents had Recombinant: -different combination of linked alleles than in parents -Product of recombination or crossovers during meiosis in parents
What is Exceptional Progeny (mutants)? "also known as rare progeny"
Rare events of chromosome nondisjunction (we will look specifically at fruit flies)
Describe Recombination of genes
Recombination of genes linked on a chromosome occurs through physical exchange of chromosomes segments between homologs
What are reciprocal cross?
Repeat cross with opposite parental phenotypes (switch male & female phenotype/genotypes)
What is Meiosis?
Sex (gamete - egg/sperm) cells -2n gets split into FOUR HAPLOID cells -forms gametes -this is how genetic information is passed from parent to offspring
True/False: Crossing over is more likely to occur between genes that are farther apart on the chromosomes
TRUE: crossing over requires space -more likely to occur between distant genes than close genes
You cross a truebreeding white mouse to a blanca mouse. All of the F1 are agouti (wildtype). What is the best explanation?
The white mutant and blanca mutant are mutations in different genes
Describe Probability (in terms of predicting; pedigree)
We can predict the probability of an individual producing a gamete or a mating producing a child with a certain genotype or phenotype
The wildtype fruit fly is dominant in eye color (red) over the mutant (white) list the phenotypes of the given genotypes: a.)ww b.)w+w c.)w+w+
a.)White-eye b.)Red-eye c.)Red-eye
a.)Yellow flowers are dominant to white flowers. When a certain yellow-flowered plant was self-pollinated, its progeny consisted of 77 yellow and 25 white-flowered plants. What was the genotype of the original flowered parent? (YY, Yy, yy, either YY or Yy) b.)Of the 77 yellow-flowered progeny from the selfing in question a, what proportion will breed true? c.)If the original yellow-flowered parent (was heterozygous) had been used in a test cross (instead of selfing), what is the expected genotypes, and proportions of the progeny?
a.)Yy -1 big and 1 small needed b.)1/3 -tricky because its asking of the yellow-flowered progeny so of the 3 flowers that breed yellow, 1 will be true-breeding c.)1/2 Yy and 1/2 yy -because test cross is cross with homozygous recessive
Clicker Question: You are working at the UC Davis Olive Center studying whether olive pigment affects olive oil taste. From a forward genetics screen you have isolated two pigment mutants that are pale green (black is the wildtype color) and name your mutants avocado and pistachio. You do the following crosses and observe the given progeny phenotypes (cross 1 and cross 2 parents are true-breeding): Cross 1: avocado x pistachio F1 all pale green Cross 2: avocado x wildtype F1 all dark green Cross 3: self F1 from cross 2 F2 4 black:10 dark green: 3 pale green What can you conclude based on the crosses above?
avocado and pistachio are mutant alleles of the same gene
What is an allele series?
different alleles of same gene with different degrees of gene function, you can order the alleles relative to one another for dominance **Hierarchy of dominance**
Difference between a dihybrid cross and a dihybrid test cross
dihybrid = heterozygous for both genes testcross = cross of your individual of interest with a homozygous recessive individual
What is Meiotic non-disjunction?
errors in chromosome segregation in Meiosis -meiotic error
What is a DNA sequence?
the order of nucleotides in DNA -Ex: C, A, E, R: RACE vs CARE -Ex: A, G, T: ATG vs GTA