Section 1
Preview this deck
A pea plant heterozygous for inflated pods (Ii) is crossed with a plant homozygous for constricted pods (ii) . Draw a punnet square for the cross.
Front
| 5 | 0 | ||
| 4 | 0 | ||
| 3 | 0 | ||
| 2 | 0 | ||
| 1 | 0 |
Active users
0
All-time users
0
Favorites
0
Last updated
6 years ago
Date created
Mar 14, 2020
Cards (74)
Section 1
(50 cards)
A pea plant heterozygous for inflated pods (Ii) is crossed with a plant homozygous for constricted pods (ii) . Draw a punnet square for the cross.
I i i Ii ii i Ii ii
Why peas?
Several differnet variants, short generation time, and large number of offspring from each mating; could strictly control mating between plants; only tracked those characters that varied between two distinct alternatives; only purple or white, no intermediates Used True breeding (Plants only gave rise to purple plants)
List the different gametes that could be made by a plant heterozygous for seed color, seed shape, and pod shape. how large a punnett square would you need o predict the offspring of a self-pollination of this trihybrid?
Plant could make 8 different types of gametes (YRI, YRi, YrI, YrI, yRI, yRi, yrI, and yri to firt all the possible gametes the punnett square would have to be 8 x 8 or 64 squares
Tay Sachs disease
an inherited disorder in humans in which the brain cells of baby can not metabolize certain lipids because a crucial enzyme does not work properly. Accumulation of these lipids in brain, causes seizures, blindness and degeneration of motor. Only children that inherit two copies of the Tay-Sachs allele develop the disease.
F2 generation
Allowing the F1 hybrids to self-pollinate produces this generation Need F2 to see the basic patterns of inheritance
Epistasis
A second gene determines whether or not the pigment will be deposited in the hair. The dominant allele symbolized by C (color) This allele deposits either black or brown pigment. The color deposition depends on the genotype at the first locus. But if the mice is homozygous recessive for the second locus (cc), then the coat is white (albino) The gene for pigment is epistatic to the gene that codes for black or brown pigment
Genotype BbDD is mated with the gentotype BBDd. Write genotypes of all possible offspring form this cross
1/4 BBDD; 1/4 BbDD; 1/4 BBDd; 1/4 BbDd
law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation (only applies to genes located on different chromosomes) derived by following two characters at the same time, like seed color and seed shape; seeds can be either green or yellow and round or wrinkled; Found yellow seed was dominant and same with round
dihybrids
heterozygous for two characters Mixed YYRR (homozygous for dominant trait-yellow and round) with yyrr (homozygous for recessive allele) F1 generation is YyRr
How did Mendel discover the basic principles of heredity?
By breeding peas in carefully planned experiments ; monastery provided fertile ground in more than one ways for mendel's study of inheritance
F1
First hybrid offspring (first filial generation "son")
Punnett square
shows all possible combination of alleles in offspring that result from F1 x F1 cross
homozygous
pair of identical alleles for a character is said to be homozygous for the gene controlling that character; P generation, homozygous for PP for purple dominant allele White plant is homozygous for that gene (pp) Breed True;
Incomplete dominance
the F1 hybrids have phenotype intermediate between that of the parents F2 shows 1:2:1 phentoypic ratio The alleles of some characters fall in the middle of the spectrum of dominance. The F1 hybrids have a phenotype some where in between the phenotypes of the two parental varieties
Solving genetic problems with rules of probability
The probability of a particular genotype arising from a cross can be determined by considering each gene involved as a monohybrid cross Multiplying the probabilities of all the independent events involved in the final genotype When more than one outcome is involved, the addition rule is also used
Trait
Each variant for a character such as purple or white flowers
Mendel's model to explain the 3:1 inheritance pattern
1. Alternative versions of genes account for variations in inherited characters (This means that the gene for flower color in pea plant exist in two versions: One for purple flower One for white flower) 2. For each character, an organism inherits two alleles (one from each parent) 3. If the two alleles at a locus differ, then the dominant allele determines the organism's appearance (phenotype) The recessive allele has no noticeable effect on organism's phenotype 4. Known as law of segregation, states that the two alleles for a character are packaged into separate gametes Thus an egg or a sperm gets only one of the two alleles that are present in the somatic cell of the organism. This interpretation is consistent with the behavior of chromosomes during meiosis
How do we determine the probability that two or more independent events will occur together
Law of multiplication What is the chance that two coins tossed simultaneously will both land on head or tail? Multiply the probability of one coin coming up head (1/2) x the probability of the second coin coming up head (1/2)=1/4 This means that the chances of having two heads is 25% This same rule applies to F1 monohybrid cross
Co-dominance
Both alleles affect the phenotype in separate, distinguishable ways (MN blood group)
monohybrids
they were heterozygous for one character, cross between such heterozygous as monohybrid cross Mendel derived his law of segregation from experiments which he followed only a single character, such as flower color
Pic for law of independent assortment
YyRr x YyRr
The probability of a monohybrid cross of color Yy x Yy= YY (1/4), yy (1/4) and Yy (1/2). The same probability applies to the offspring genotype for seed shape. The probability of a monohybrid cross of color Rr x Rr= RR (1/4), rr (1/4) and Rr (1/2). We can simply use the multiplication rule to determine the probability of each of the genotypes in the F2 generation. So the probability of an F2 plant having YYRR genotype would be ¼ x ¼=1/16
P Generation
the true breeding parents
What governs Mendelian inheritance?
law of probability Mendelian laws of segregation and independent assortment reflect the same rules that apply to tossing a coin. The probability ranges from 0 to 1. An event that is certain to occur has the probability of 1 An event that is certain not to occur has a probability of 0
Other parts of Mendel's experiment where he found the save 3/4 1/4 ratio
axia terminal flower position, seed color, seed shape, pod shape, pod color, stem length Mostly 3:1
Incomplete dominance and epistasis are both terms that define genetic relationships. What is the most basic distinction between this terms?
Incomplete dominance describes the relationship between two alleles of a single gene, whereas epistasis relates to the genetic relationship between two genes (and the respective alleles of both)
Test cross
Suppose we have a pea plant that has purple flowers. We can not tell from its flower color if this plan is homozygous or heterozygous because the genotype PP or Pp results in the same phenotype. So how can we test the genotype of the plant? To determine genotype--we can cross this plant (PP) with white-flower plant (pp) which will make only gaemets with the recessive allele; if all of the phenotypes are purple, it was dominant (produced Pp); if heterozygous (will get some white flowers, 1 at least)
Sum Rule
The probability of either one of the two independent events is the sum of their individual probabilities LOOK FOR WORD OR Example: Dice probability of 2 fours or 2 fives (1/6)(1/6) + (1/6) (1/6)= 2/36 or 1/18
Three characters (flower color, seed color, and pod shape) are considered in a cross between two pea plants (PpYyIi x ppYyii) What fraction of the offspring would be predicted to be homozygous recessive for at least two of the three characters?
3/8s (1/16)+ (2/16)+ (1/16)+ (1/16)+(1/16)= 3/8
phenotype
appearance, observable traits
alleles
alternative versions of a gene
Pleitropy
mutliple phenotypic effects of genes Pleiotopic alleles are responsible for multiple symptoms associated with cystic fibrosis and sickle cell disease
Product rule
The chance of any number of things happening together is equal to the product of the chances of each happening separately. Independent events; LOOK FOR WORD AND 3 heads in toss of 3 coins: 1/2 x 1/2 x 1/2= 1/8
genotype
genetic make up
Complete dominance
the phenotype of heterozygous is indistinguishable form that of the dominant homozygous
Character
a heritable feature that varies among individuals, such as flower color
For any gene with a dominant allele C and recessive allele c what proportions of the offspring form a CCx Cc cross are expected to be homozygous dominant, homozygous recessive and heterozygous?
2:2 (2 heterozyous and 2 homozygous dominant)
Many human traits
do follow mendelian patterns of inheritance; like widows peak (dominant allele)
A rooster with gray feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks are grey, 6 are black, and 8 are white. What is the simplest explanation for the inheritance of these colors in chickens? What phenotypes would you expect in the offspring between gray and black hen?
The black and white alleles are incompletely dominant, with heterozygous being gray in color; a cross in gray and black would yield equal black and gray
Results of Mendel's experiment
P: Purple F1: all purple F2 1/4 white, 3/4 purple Therefore white flower trait didn't disappear, it was just masked when purple flower was present
Hybridization
crossing/mating of two true-breed varieties Mendel cross-pollinated two contrasting, true-breeding pea varities (purple and white flowers)
If a man with type AB blood marries a woman with type O blood, what blood types would you expect in their children?
1/2 A; 1/2 B
genotype vs. phenotype
Blending model
the F1 hybrids would be a cross between purple and white flowers; so they would be pale purple; a trait intermediate between those of the P generation
dominant trait
purple flower; determines organisms appearance
recessive
white flower; has no noticeable effect on the organisms appearnce
True breeding
varieties that, over many generations of self-pollination, had produced only the same variety as the parent plant.
heterozygous
an organism that has two different alleles for a gene; not true-breeding because they produce gametes with different alleles
Probability
# of times an event is expected to happen or # of opportunities for an event to happen Range: 0 to 1 Examples: Dice; probability of rolling 6
Pea plant heterozygous for flower position and stem length AaTt are allowed to self pollinate and 400 resulting seeds are planted. Draw a punnet square. how many offspring would be predicted to have terminal flowers and be dwarf?
25 (1/16)
Section 2
(24 cards)