Biology genetics section
What are the 3 basic "flavors" of dominance within alleles?
1. Complete Dominance 2. Incomplete Dominance 3. Co-dominance
What are the 2 Rules of Probability?
1. Rule of Multiplication 2. Rule of Addition
AaBbCc x AaBbCc What is the probability of getting bb?
1/2 probability from parent 1 1/2 probability from parent 2 overall: 1/2 x 1/2 = 1/4
You are examining a trait which shows three distinct phenotypes, with the phenotype of heterozygotes expressing both alleles seen in the homozygotes. This is an example of: A) Codominance. B) Complete dominance. C) Incomplete dominance. D) Pleiotrophy.
A) Codominance
A person who is heterozygous for the B allele and the O allele, has blood type..
B
Two F1-hybrid plants with yellow, round seeds (YyRr) are crossed. What is the probability of getting an offspring with the genotype YYRr? A) 4/8 B) 1/8 C) 1/16 D) 2/8 E) 3/16
B) 1/8
Two F1-hybrid plants with yellow, round seeds (YyRr) are crossed. What is the probability of getting an offspring with the genotype YYRr? A) 4/8 B) 1/8 C) 1/16 D) 2/8
B) 1/8
You cross two, true-breeding parents (one with yellow peas and one with green peas). All of the F1 progeny (offspring) have yellow peas. You grow and self-pollinate this F1 generation and collect 1600 F2 progeny. How many plants with yellow peas would you expect? A) 1600 B) 1200 C) 800 D) 400
B) 1200
In fruit flies (Drosophila), an autosomal gene controls body color. Individuals that are homozygous recessive have an ebony body color but are quite weak. Individuals that are homozygous dominant have a normal body color and normal physical condition and heterozygous individuals have a normal body color with increased physical condition. This is an example of A) epistasis. B) heterozygote advantage. C) polygenic inheritance. D) multiple alleles.
B) heterozygote advantage
If a person with blood type A and a person with blood type B have a child, what are the possible blood types that child could have? A) Only type AB is possible B) Types A and B are possible C) Types A, B, AB, and O are possible D) Types A, B, and AB are possible
C) Types A, B, AB, and O are possible
__________________ is a human genetic disease that results in mental retardation, but it can be prevented by following a strict low-protein diet. A) Cystic fibrosis B) Sickle-cell anemia C) Huntington's disease D) Phenylketonuria
D) PKU
What is the probability of an individual with the genotype IAi producing a child with type O blood? A) 1 (100%) B) 1/2 (50%) C) 1/4 (25%) D) The question can't be answered with the information given.
D) The question can't be answered with the information given.
An individual that is heterozygous for an allele and that exhibits a phenotype intermediate between that of the two homozygous alternatives is an example of _____. A) polygenic inheritance B) pleiotropy C) codominance D) incomplete dominance E) epistasis
D) incomplete dominance
What possible blood types could offspring have if their two parents have the blood types A and AB, respectively? A) AB only B) A, B, AB, and O C) A and O only D) A and B only E) A, B, and AB only
E) A, B, and AB only
What is the difference, including the number of genes difference, between Epistasis & Pleiotropy?
Epistasis involves at least two genes; one gene controls expression of another gene(s), and only one aspect of the phenotype. Pleiotropy involves a single gene but this gene impacts more than one aspect of an organisms' phenotype.
What was Mendel's second conclusion about diploid individuals?
For an individual inheriting 2 different copies of alleles (alternative forms of a gene), one will be dominant and one will be negative.
The alleles that an individual has determine its __________, it's genetic composition (the alleles it has) of an individual.
Genotype. Ex. a pea plant with white flowers has two copies of a white allele. most organisms we deal with are diploids, which means that they have two copies of each chromosome and two copies of each gene on those chromosomes.
If one parent who has Huntington's disease is heterozygous for the trait and the other parent is not affected, what are the chances of their offspring inheriting the trait? A) 50% B) 100% C) 0 D) 25%
Hh + hh A) 50%
describe the interrelationships between parents and children, over generations, regarding a specific trait.
Human pedigrees.
In the P generation, there is one red flower and one white flower. In the F1 generation, these two parents create a pink flower. What kind of dominance is this representing?
Incomplete dominance.
Pedigree analysis: squares refer to... circles refer to...
Males Females
the father of genetics
Mendel mid 1800s
The human ABO blood group has 3 alleles, an example of...
Multiple Alleles.
Are most genetic traits determined by a single gene?
NO!!! most traits are what we term "Polygenic"
Autosomal
Non sex linked
Contrast a Punnett square with Pedigree analysis:
Pedigrees look into the past, Punnett squares make predictions about future offspring.
The frizzle gene in chickens: the gene causes: abnormal body temperature, frizzy looking feathers, higher metabolic and blood flow rates and a greater digestive capacity. Caused by a single gene that has multiple affects on the organisms phenotype. This is an example of..
Pleiotrophy
Sometimes a gene can have an effect on more than one aspect of an organisms' phenotype, which is referred to as..
Pleiotropy
skin color in humans is a trait that is controlled by many genes, referred to as a..
Polygenic trait
traits that are controlled by many genes.
Polygenic traits
What was Mendel's third conclusion?
Recessive traits are only expressed if an individual has 2 recessive alleles. (homozygous recessive)
Sickle Cell Disease: the gene that tells your body to make hemoglobin is mutated. Hemoglobin is a component of every red blood cell, it allows red blood cells to carry oxygen from your lungs to all parts of your body, and to carry carbon dioxide waste from throughout your body to your lungs so that it can be exhaled. Symptoms: Mode of inheritance:
Symptoms: Red blood cells become rigid, sticky & are shaped like sickles, they get stuck in small blood vessels, which can slow or block blood flow & oxygen to parts of the body. Mode of inheritance: Recessive (Autosomal Recessive Disorder)
Huntington's Disease: a progressive, degenerative disease that causes nerve cells in your brain to waste away. Symptoms: Mode of inheritance:
Symptoms: leads to uncontrolled movements, emotional disturbances and mental deterioration. Signs develop in middle age usually. Mode of inheritance: Dominant Autosomal disorder
On pedigrees, is birth order indicated?
YES! from left to right.
An organism with two white ___________, has the __________ of white flowers.
alleles; phenotype
Relationships between alleles are/are not always dominant/recessive.
are not!!
If the square or circle is _________, the individual is termed normal and does not exhibit the trait that is being analyzed in the Pedigree.
empty
If the square or circle is ___________, the individual is termed to be affected with the trait.
filled in.
Flower color in a pea plant is the result of a ________.
gene.
In a Monohybrid cross, we are tracking the inheritance of a
single trait.
If the square or circle is ____________, that indicates that the individual is a carrier; an individual that carries a recessive allele but is phenotypically normal, they are heterozygous for a recessive condition.
half filled in
allows us to determine the genotype of an organism of unknown genotype.
test cross
AaBbCc x AaBbCc What is the probability of getting cc?
1/2 probability from parent 1 1/2 probability from parent 2 overall: 1/2 x 1/2 = 1/4
AaBbCc x AaBbCc What is the probability of getting a aa?
1/2 probability from parent 1 1/2 probability from parent 2 overall: 1/2 x 1/2 = 1/4
AaBbCc x AaBbCc What is the overall probability of getting aabbcc? aa = 1/4 bb = 1/4 cc = 1/4
1/4 x 1/4 x 1/4 = 1/64
What is the probability of rolling a 5 and then a 3 with a fair die?
1/6 x 1/6 = 1/36
If you have F1 individuals with the genotype AaBbCc that self fertilize, what is the probability of each of these genotypes in their offspring? aabbcc
1/64 (explained further)
For multiple genes and their alleles, probability theory is an easier way than the punnet square to predict future offspring. T or F?
True!
With recessive traits, children need to inherit two copies of the gene, one from each parent, in order to have the disease. T or F?
True!!
In a dihybrid cross, our Punnet Square is ___ squares.
16 squares (4 by 4)
In incomplete dominance, there is a 1:2:1 genotypic ratio (like in complete dominance), but the difference is that there is NOW a ____________ phenotypic ratio, unlike complete dominance.
1:2:1 phenotypic ratio 1 the same as parent A 1 the same as parent B 2 are the mixed result of B + A
A person who is heterozygous for the A allele and the O allele, has blood type..
A
Both alleles contribute equally to phenotype; no masking
Co-dominance results in a completely unique phenotype in the heterozygote.
In _____________, the heterozygote has a unique phenotype AB blood group, has both the A and B allele.
Codominance
Both A and B are completely dominant to allele ____.
O
In the ___________, there are only TRUE-BREEDING parents.
P Generation
First generation cross, the parental cross, is known as the...
P generation (the true-breeding parents) ex. One purple flower and one white flower start off.
Say whether the following are homozygous or heterozygous: PP: Pp: pp:
PP: homozygous Pp: heterozygous pp: homozygous
Genetic variation within a population are due to..
alleles.
How do you calculate the number of different allele combinations produced during meiosis?
2^n = # of different allele combinations n = # of heterozygous genes.
According to Mendel's Law of Independent Assortment, an individual with genotype (Rr, Gg) that is Heterozygous for Rr and Gg can produce how many different gamete types?
4 rg RG rG Rg
A true-breeding pea plant with wrinkled seeds (rr) is crossed with a pea plant that is heterozygous for round seeds (Rr). What portion (expressed as a decimal) of the offspring should have round seeds? A) 0.50 B) 0 C) 1.00 D) 0.25 E) 0.75
A) 0.50
If the P generation is AABBCC x aabbcc, what is the probability of getting an offspring with genotype AaBbcc in the F2 generation? A) 1/16 B) 1/8 C) 3/16 D) 1/64
A) 1/16
What is the probability of a pea plant with genotype RrYy producing a gamete with genotype ry? A) ¼ B) ½ C) ¾ D) 1
A) 1/4
Given the counts below, what is the ratio of purple:white flowers in the following example? Purple = 770 White = 222 A) 3.47:1 B) 992:1 C) 548:1 D) 0.29:1 E) 0
A) 3.47:1
In a cross of two F1-hybrid plants with purple flowers and round seeds (PpRr), what fraction of the offspring should have purple flowers and round seeds (purple flowers and round seeds are the dominant traits)? A) 9/16 B) 1/12 C) 1/16 D) 3/16 E) 12/16
A) 9/16
To determine if a plant with purple flowers is homozygous (PP) or heterozygous (Pp) for that trait, one would do a test cross with plants of the _____ genotype. A) pp B) PP C) Pp D) p E) P
A) pp
a variant of a gene that is responsible for the variation in the character (e.g. purple flowers vs. white flowers)
Allele
How many different gamete types can an individual with genotype aaBBCcDd make? A) 2 B) 4 C) 8 D) 16
B) 4
Your friend wants to have four children. What is the probability that she will have 3 girls and 1 boy? A) 1/16 B) 1/8 C) 4/16 D) ½
C) 4/16
Two F1-hybrid plants with purple flowers and round seeds (PpRr) are crossed. If 1,000 randomly chosen offspring from this cross are examined, how many should have white flowers and wrinkled seeds (purple flowers and round seeds are the dominant traits)? You may need to round off your answer to the nearest whole number. A) 83 B) 563 C) 63 D) 750 E) 188
C) 63
Which of the following would Mendel have described as a character for pea plants? A) tall stems B) round seeds C) stem length D) purple flowers E) wrinkled seeds
C) stem length
In a ____________, both alleles are equally expressed in the phenotype.
Codominance
If a person has an A allele and a B allele coding for blood sugar (blood type), they then have both. Their blood type would be AB. This is an example of what kind of dominance?
Codominance.
The fruit fly Drosophila melanogaster has 3 pairs of autosomal chromosomes and an X and Y chromosome (males are XY, females are XX). How many different chromosome combinations are produced by independent assortment in D. melanogaster? A) 3 B) 4 C) 8 D) 16
D) 16
Two plants have different phenotypes and genotypes. One is heterozygous while the other is true-breeding for the same trait. You cross these two plants. What will be the phenotype of the progeny? A) Can't tell. It depends on whether the trait is dominant or recessive. B) All plants will exhibit the phenotype of the true-breeding plant. C) All plants will exhibit the phenotype of the heterozygote. D) Half will show the phenotype of the true-breeding plant, half will show the phenotype of the heterozygote.
D) Half will show the phenotype of the true-breeding plant, half will show the phenotype of the heterozygote
Which of the following is not a character in pea plants? A) stem length B) flower color C) seed shape D) green pods E) flower position
D) green pods
The generation that results from the cross of the two P Generation true-breeding parents is known as..
F1 Generation (hybrids)
How gene R assorts into gametes is dependent/independent as to how gene Y assorts into gametes.
INDEPENDENT.
Mendel proposed that the discrete units for a given character would segregate away from one another during gamete production (e.g., individuals that were heterozygous with purple flowers could produce gametes with either a white or purple factor, but not both). This is often referred to as the __________________.
Law of Segregation
this father of genetics tracked the inheritance of traits between generations. particularly in peas
Mendel
When an individual produces gametes, the alleles segregate into different gametes. This is known as the ____________.
Mendel's Law of Segregation
The examples that we have looked at thus far have had only two alleles. Many genes, however, have more than 2 alleles in the population. A situation referred to as...
Multiple Alleles
the physical characteristics of an individual (determined by genotype and sometimes the environment)
Phenotype
The F2 generation has a 3 to 1 ___________ ratio
Phenotypic ratio ex. three pink flowered plants to one white flowered plant
*An individual has genotype AaBbCc. How many different gamete types can this individual make with respect to these genes?
The answer is 8. There are 3 genes that are heterozygous in this problem. 2^3 = 8 3 = # of heterozygous genes.
The only way to determine the relationship between alleles is by analyzing the ___________.
heterozygotes.
Explain the Rule of Multiplication:
To determine the probability of an event occurring, determine the individual probabilities of each independent event, and then multiply the individual probabilities to obtain the probability of these events occurring together.
What happens during a test-cross?
cross the individual of unknown genotype and of known genotype (homozygous recessive) * this type of analysis only works with organisms which have large amounts of offspring.
what was Mendel's first conclusion about diploid individuals?
each diploid individual has two copies of each gene, 1 maternal and 1 paternal.
having two alleles that are the same
homozygous
Explain the Rule of Addition:
if an event can occur in more than one way, the probability of that event occurring is equal to the sum of the probabilities of each different way that the event can occur.
What does true breeding mean?
if you cross a true breeding purple flowered plant with itself (something possible; self-fertilization) it will only produce purple flowered plants, it breeds "true" to the purple flower characteristic. same with white flowered plant. will only breed white flowers if it is breeding with itself.
When is the only time that a recessive gene is expressed? (ex. Pp, PP, pp?)
in individuals that have two copies of the RECESSIVE allele. (Homozygous recessive = pp)
A cross between the plants of the F1 Generation results in...
the F2 Generation
Each diploid individual has how many alleles MAX?!
2 maximum for diploids.
How many different gamete types can AaBbCc parent make?
3 heterozygous genes 2^3 = 8 The punnett square would be 8 gametes by 8 gametes = 64 squares.
Case Study Question: Fur color in Labrador retrievers is determined by two genes (gene B for coat color and gene E for deposition of pigment). Nose, lip and gum color is determined only by gene B. A yellow female with brown nose and gums is mated with a brown (chocolate) male whose mother was yellow. What are their possible offspring? A) ½ yellow and ½ brown - all with brown noses. B) ½ yellow and ½ brown - all with black noses. C) 1/3 yellow and 1/3 black and 1/3 brown - all with black noses. D) ½ brown with brown noses and ½ black with black noses.
A) 1/2 yellow and 1/2 brown -- all with brown noses
Which meiotic process results in the Law of Segregation? A) Homologous chromosomes separate during Meiosis I. B) Homologous chromosomes undergoing crossing over during Meiosis I. C) Non-homologous chromosomes segregating into daughter cells independently of each other during Meiosis I.
A) Homologous chromosomes separate during Meiosis I.
An individual who is heterozygous for gene R (Rr) produces two types of gametes in regard to these alleles: R and r. This illustrates A) The Law of Segregation B) The Law of Independent Assortment C) Both the Laws of Segregation and the Law of Independent Assortment. D) The alignment of nonhomologous pairs of chromosomes during Metaphase I
A) The Law of Segregation
A plant that is true-breeding for a particular trait would __________. A) be homozygous for that trait B) show different traits in the F1 generation when crossed with itself C) be heterozygous for that trait D) carry two different alleles for that trait
A) be homozygous for that trait
Mice with the genotypes BBCc and bbcc are crossed. The alleles for brown coat (b) and no pigment (c) are recessive, and black coat (B) is dominant. What color of mice would NOT be produced by this mating? A) brown B) white C) black
A) brown
If both parents are carriers of an recessive inherited trait, what are the chances that their child will express that trait? A) 50% B) 25% C) 0 D) 100%
B) 25% Feedback: Correct. If one crosses two carriers, Hh and Hh, one should see that there is a 25% chance of the offspring being homozygous recessive (hh) for the trait.
You cross two true-breeding parents (one with purple flowers and one with white flowers). All of the F1 progeny (offspring) have purple flowers. You grow and self-pollinate this F1 generation and collect 500 F2 progeny. How many purple flowers should be produced? A) 167 B) 375 C) 0 D) 500 E) 125
B) 375
Does the Law of Independent Assortment apply to a single character (gene)? A) Yes B) No
B) No! *The Law of Independent Assortment describes the behavior of non-homologous chromosomes during meiosis. The alleles of a single gene do not assort independently of each other - they are segregated according to the Law of Segregation.
__________ is an example of a character that is controlled by more than one gene (a quantitative character) and demonstrates a continuum of phenotypes. A) Pleiotropy B) Polygenic inheritance C) Epistasis D) Codominance E) Incomplete dominance
B) Polygenic inheritance
You have two rose plants, both with pink flowers. You cross the two plants and are surprised to find that, while most of the offspring are pink, some are red and some are white. You decide that you like the red flowers and would like to make more. What cross would you perform to produce the most red flowered plants? A) Pink x pink B) Red x white C) Red x red D) White x pink
B) Red x white
_______ is an example of a recessive inherited trait. A) Huntington's disease B) cystic fibrosis C) Brachydactyly. D) The AB blood type
B) cystic fibrosis
In a cross between a true breeding purple pea plant and a true breeding white pea plant A) the white trait is not present in the F1 generation. B) the purple trait is completely dominant to the white trait. C) both the white trait and the purple trait are expressed in the phenotype at the same time in an F1 individual. D) the F1 individuals have a phenotype that is intermediate between purple and white.
B) the purple trait is completely dominant to the white trait
A plant with purple flowers and round seeds (PpRr) is crossed with a plant with white flowers and wrinkled seeds (pprr). What fraction of the offspring should have white flowers and wrinkled seeds? (Purple flowers and round seeds are dominant.) A) 1/5 B) 3/4 C) 1/4 D) 1/3 E) 1/2
C) 1/4
In water snakes, body color is controlled by two alleles that display incomplete dominance. Snakes with the BB genotype are brown, those with the Bb genotype are gray, and individuals with the bb genotype are green. If a brown snake and a gray snake are crossed, what ratio of phenotypes should be expected in the offspring? A) 1:1, gray:green B) 1:2:1, brown:gray:green C) 1:1, brown:gray D) 1:1:1, brown:gray:green E) 1:1, brown:green
C) 1:1:1, brown: gray: green
The gene controlling ear color in a gizmo has two alleles that exhibit incomplete dominance: CR, which codes for red ears; and CY, which codes for yellow ears. Individuals that are homozygous for the CR allele have red ears, whereas the heterozygous genotype produces orange ears. Those that are homozygous for the CY allele have yellow ears. If two individuals with orange ears are crossed, what ratio of phenotypes should be expected in the offspring? A) 9:3:1, red:yellow:orange ears B) 3:1, red:yellow ears C) 1:2:1, red:orange:yellow ears D) 1:2:1, red:yellow:orange ears E) 1:3, red:yellow ears
C) 1:2:1, red:orange: yellow ears
Which meiotic process results in the Law of Independent Assortment? A) Homologous chromosomes separating during meiosis I. B) An individual that is heterozygous for a gene producing two different gamete types for that gene. C) Non-homologous chromosomes segregating into daughter cells independently of each other. D) Homologous chromosomes segregating into daughter cells independently of each other.
C) Non-homologous chromosomes segregating into daughter cells independently of each other.
The effects of _________ can be almost completely overcome by regulating the diet of the individual from infancy. A) cystic fibrosis B) sickle-cell disease C) phenylketonuria (PKU) D) Huntington's disease
C) PKU *PKU involves the inability to metabolize phenylalanine. Individuals with the disorder can avoid that amino acid, and thus avoid the effects of the disorder.
Pedigrees reveal that a trait shows a dominant pattern of inheritance if that trait _______. A) skipped generations B) was lethal C) did not skip generations D) was only inherited by males
C) did not skip generations
A gene that affects the expression of a second gene is an example of _____. A) pleiotropy B) codominance C) epistasis D) polygenic inheritance E) incomplete dominance
C) epistasis
In squash, color is determined by two genes that are epistatic. At the first gene, white squash (W) is dominant to colored squash (w). At the second gene, yellow (Y) is dominant to green (y). A squash that is green must have the genotype: A) WWyy B) Wwyy C) wwyy D) A green squash can be either Wwyy or WWyy.
C) wwyy
Also referred to as "Mendelian inheritance"
Complete Dominance
In _______________, the heterozygous individual is indistinguishable from the homozygous dominant individuals. purple flowered pea plants can either be heterozygous or homozygous dominant. You cannot tell the difference by just looking at them.
Complete dominance
One allele (dominant) completely masks others (recessive)
Complete dominance
You cross two true-breeding parents (one with yellow seeds and one with green seeds), grow and self-pollinate the F1 generation, and then count the number of offspring with yellow and green seeds. If you counted 2,000 offspring and there was a 3:1 ratio of yellow:green seeds, how many offspring would have yellow seeds? A) 500 B) 667 C) 1999 D) 1,500 E) 1,000
D) 1,500
Which of the following genotype(s) would result in an individual with the type A blood phenotype? A) ii B) IA IA C) IA i D) Both b and c E) All of the above
D) Both b and c
You have a pea plant that exhibits the dominant trait of green pods. You cross this plant to a true-breeding plant with the recessive trait of yellow pods. Half of the offspring from this cross have green pods and the other half have yellow pods. Which of the following statements is true? A) The parent with green pods was true-breeding for green pods. B) The parent with yellow pods was heterozygous for this character. C) The parent with green pods had the genotype GG. D) The parent with green pods had the genotype Gg. E) The parent with yellow pods had the genotype Gg.
D) The parent with green pods had the genotype Gg.
When Mendel crossed a true-breeding purple-flowered pea plant with a true-breeding white-flowered pea plant, he observed that all of the F1 offspring had purple flowers. When these F1 plants were selfed, he found 3/4 were purple and 1/4 were white. Which of the following observations supports Mendel's conclusion that each progeny can carry two alternative copies of a "factor"? A) When the white progeny are selfed, only white progeny result. B) When the purple progeny are crossed with the white progeny, only purple progeny result. C) When the purple progeny are selfed, only purple progeny result. D) When the purple progeny are selfed, both white and purple progeny result.
D) When the purple progeny are selfed, both white & purple progeny result.
You are given two plants. One plant is tall and the other is short. You cross these parentals and find all F1 progeny are tall. You cross the F1 progeny with one another and find the resulting F2 generation is composed of 770 tall plants and 300 short plants. You should conclude that ___________. A) both parental plants are homozygous, and short is dominant to tall B) both parental plants are heterozygous, and short is dominant to tall C) you can't tell from the information given D) the F1 plants are heterozygous, and tall is dominant to short E) the F1 plants are homozygous, and tall is dominant to short
D) the F1 plants are heterozygous, and tall is dominant to short
the material that chromosomes are made from
DNA
tracks the inheritance of two traits. like looking at seed color & seed shape.
Dihybrid cross
If two F1-hybrid pea plants with purple flowers (Pp) are crossed, what portion (expressed as a decimal) of their offspring would have white flowers (purple flowers are the dominant trait)? A) 0 B) 0.50 C) 1.00 D) 0.75 E) 0.25
E) 0.25
You cross two true-breeding parents, one with purple flowers and one with white flowers, grow and self-pollinate the F1 generation, and then count the number of offspring with purple and white flowers in the F2 generation. If you counted 1,200 offspring and there was a 3:1 ratio of purple:white flowers, how many offspring would have purple flowers? A) 1100 B) 75 C) 300 D) 25 E) 900
E) 900
Mendel's Law of Independent Assortment states that _____. A) the two alleles for a character segregate during gamete production B) his Law of Segregation is not always true C) offspring inherit traits from their parents D) homologous chromosomes pair up during Prophase I of meiosis E) the alleles for different characters segregate randomly from one another during gamete production
E) the alleles for different characters segregate randomly from one another during gamete production
a relationship between at least two genes and one gene affects expression of another gene(s) Coat color in horses. there are two different genes that play a role in determining coat color: Gene B coats for pigment, B for black, b for brown. Gene C is epistatic on Gene B & determines whether or not Gene B gets expressed. Gene C (big C) allows the pigment to be deposited. *If the horse has two cc (recessive homozygous) then there will be absolutely NO pigment delivered. Those horses will be a white color.
Epistasis
How many genes are involved in Epistasis? How many genes are involved in Pleiotropy?
Epistasis: at least 2 genes Pleiotropy: a single gene
a piece of DNA (the material that chromosomes are made from) that codes for a specific character in an organism (e.g. flower color in pea plants)
Gene
In the F2 Generation, the ___________ ratio is 1 to 2 to 1. One homozygous dominant, to 2 heterozygotes, to one homozygous recessive.
Genotipic ratio
In Mendel's experiments, the F1 generation always contains homozygous/heterozygous genes?
Heterozygous can make a Pp and a Pp
In ___________, the heterozygote has a phenotypes that is intermediate between the two homozygotes. Red + White = Pink
Incomplete Dominance
Both alleles contribute to phenotype of the individual, but heterozygote is intermediate to either homozygote (i.e. in monohybrid cross, three phenotypes are observed)
Incomplete dominance
Is it possible for someone to be a carrier for a dominant trait?
NO. If you have the dominant allele, you express it.
Phenylketonuria: the normal allele contains the instructions for making an enzyme needed to process the amino acid called phenylalanine; the alternative allele has a mutation & that enzyme does not get made. Amino acids are the building blocks for proteins. Without the enzyme necessary to process phenylalanine, what happens? Symptoms: Mode of inheritance:
Symptoms: a dangerous buildup of the amino acid develops when a person with PKA eats foods that are high in protein; phenylalanine builds up in the brain and causes nerve degeneration, progressive retardation. Mode of inheritance: Recessive (Autosomal Recessive disorder) People are put on a low-protein strict diet.
Cystic Fibrosis: a defective gene alters a protein that regulates the normal movement of salt in and out of cells; results in thick, sticky secretions in the respiratory & digestive tracts. Symptoms: Mode of inheritance:
Symptoms: lung damage, lung infections, nutritional deficiencies Mode of inheritance: recessive allele (an autosomal recessive disorder)
Because Huntington's disease is a DOMINANT autosomal disorder, that means that an affected person MUST have an affected parent. T or F?
TRUE!
The F1 typically shows the dominant traits, especially if you are using a dihybrid cross. T or F?
TRUE.
The fruit fly Drosophila melanogaster has 3 pairs of autosomal chromosomes and an X and Y chromosome (males are XY, females are XX). How many different chromosome combinations are produced by independent assortment in D. melanogaster?
The answer is 16 different chromosome combinations (2^4)=16 *in this example, there are 4 homologous pairs of chromosomes, the 3 homologous chromosomes and the X & Y chromosome. (the X and Y are not truly homologous but they behave like homologs during meiosis)
An individual has genotype AaBbCC. How many different gamete types can this individual make with respect to these genes?
The answer is 4. There are two heterozygous genes (gene A and gene B). Gene C is homozygous and does not result in any genetic variation. 2^2 = 4, where 2 = # of heterozygous genes.
How is it that a child can be born with cystic fibrosis?
The child must have two parents who are UNAFFECTED CARRIERS.
What is the probability of rolling a 5 when rolling 2 dice?
There are four different ways to roll a five (3+2, 2+3, 4+1, 1+4) 1/6 x 1/6 = 1/36 1/6 x 1/6 = 1/36 1/6 x 1/6 = 1/36 1/6 x 1/6 = 1/36 ___________________ 4/36 = total probability.
Incomplete dominance uses super scripts. T or F?
True.
When an organism shows a dominant/recessive trait, we cannot tell it's genotype by just looking at it.
dominant
The sickle cell allele provides protection against malaria infection, but only in carriers. This is known as a...
heterozygote advantage.
having two alleles that are different
heterozygous
Horizontal lines between a circle and square means that the two are ____________. And the vertical lines that descend from the horizontal lines indicate ________.
mating partners offspring
Dr. Mark Shriver, Department of Anthropology at PSU is working out the number of genes responsible for human pigmentation. He is using ____________, which share many of the same skin genes with humans. He is looking at the gene known as SLC24A5, a gene responsible in pigment production in fish and humans.
zebra fish
