Chapter 14/15 - Patterns of Inheritance Flashcards
The passing of traits from parents to offspring through asexual or sexual reproduction
Heredity
Heredity by means of genes assumed
traits were from ‘fluid’ like blood
The first investigator to achieve and document successful experimental hybridizations, or the mating of unlike parents
Josef Klreuter
Who in 1760 cross-fertilized (or crossed, for short) different strains of tobacco and obtained fertile offspring?
Josef Klreuter
By cross-fertilizing (or crossed, for short) different strains of tobacco Josef Klreuter produced __________
hybrids
Who observed variations different from parent
plants
Josef Klreuter
Josef Klreuter:
Hybrid offspring crosses resulted in ___________________________________
even more differences compared to the grandparents and parent plants
Who crossed garden pea plants that had either yellow or green seeds (true-breeding)?
What did this result in?
T.A. Knight (1823)
Hybrids produced yellow or green seeds (segregating)
Offspring produced from self-fertilization, remaining uniform from one generation to the next.
true breeding
Some offspring exhibit one form of a trait (yellow seeds), and other offspring from the same mating exhibit a different form (green seeds).
segregating
Was a scientist, friar and abbot
Grew up on a farm
Math and physics background allowed him to approach genetics from a mathematical standpoint
Gregor (Johann) Mendel
Mendel studied __________________________
hybrid crosses in pea plants
What characteristics did Mendel find easily distinguishable in pea plants?
shape of seeds
color of seeds
color of pods
shape of pods
plant height
position of flowers
flower color
Mendel studied hybrid crosses in pea plants due to ___________________________________
Due to true-breeding, pure varieties of each trait were available
Mendel studied hybrid crosses in pea plants because pea plants are _______________________
small and grow fast
While studying pea plants Mendel discovered that male and female parts on the same flower of the plant, allow for ____________________________
self-fertilization (retention of trait)
Mendel usually conducted his experiments in three stages: Which were?
- Mendel allowed plants of a given variety to self-cross for multiple generations to assure himself that the traits he was studying were indeed true-breeding—that is, transmitted unchanged from generation to generation
- performed crosses between true-breeding varieties exhibiting alternative forms of traits. He also performed reciprocal crosses: using pollen from a whiteflowered plant to fertilize a purple-flowered plant, then using pollen from a purple-flowered plant to fertilize a white-flowered plant.
3.Finally, Mendel permitted the hybrid offspring produced by these crosses to self-fertilize for several generations, allowing him to observe the inheritance of alternative forms of a trait. Most important, he counted the numbers of offspring exhibiting each trait in each succeeding generation.
.
concepts of inheritance in which traits of parents were carried by fluid and “blended” in offspring.
blending inheritance,
A cross that follows only two variations on a single trait, such as white- and purple-colored flowers. This deceptively simple kind of cross can lead to important conclusions about the nature of inheritance.
monohybrid cross
One trait, two variations
monohybrid cross
exhibits only one of two traits with no blending
F1 generation
When Mendel crossed white-flowered and purple-flowered plants, the hybrid offspring he observed did not have flowers of intermediate color, as the hypothesis of blending inheritance would predict. Instead, in every case the flower color of the offspring resembled that of one of their parents. These offspring are customarily referred to as the ______________________
first filial generation, or F1
No blending of traits
Always inherit same trait as one parent
first filial generation, or F1
In a cross of white-flowered and purple-flowered plants, the F1 offspring all had _________ flowers.
Mendel called these flowers the ___________ trait.
purple
purple; dominant
In Mendels experiment, what color flowers were referred to as the recessive trait
white
Mendel referred to the form of each trait expressed in the F1 plants as ________________ and to the alternative form that was not expressed in the F1 plants as _________________
dominant
recessive
exhibits a 3:1 ratio of both traits
F2 generation
After allowing individual F1 plants to mature and self-fertilize, Mendel collected and planted the seeds from each plant to see what the offspring in the ________________ generation would look like.
second filial generation, or F2,
What generation are offspring?
second filial generation, or F2,
What did Mendel find in the second filial generation, or F2?
Predominantly purple flower(75%) with reappearance of recessive white flowers (25%) , whom was hidden in F1 generation.
the dominant-to-recessive ratio among the F2 plants was always close to _________
3:1; or 1:2:1
1 true-breeding dominant: 2 not-true-breeding dominant: and 1 true-breeding recessive.
ratio of F2 plants
ratio of F2 plants
1 true-breeding dominant: 2 not-true-breeding dominant: and 1 true-breeding recessive.
Mendel performed crosses (Parents, then F1)
for all 7 traits in pea plants
– Found similar results. Describe his results___________________________
75% possessed dominant trait
25% possessed recessive trait
Further experiments by Mendel revealed that the
recessive trait was always
_____________________, F3, F4, F5 generations
always had __________flowers
true-breeding
white
⅓ of the dominant, purple-flowered F2 individuals were ________________, ____ were not.
true breeding
⅔
Mendel’s Principle of Segregation explains ___________________
monohybrid observations
Mendels Conclusions:
- plants he crossed did not produce progeny of intermediate appearance
- For each pair of alternative forms of a trait, one alternative was not expressed in the F1 hybrids, although it reappeared in some F2 individuals. The trait that “disappeared” must therefore be latent (present but not expressed) in the F1 individuals.
- The pairs of alternative traits examined were segregated among the progeny of a particular cross, some individuals exhibiting one trait and some the other.
- These alternative traits were expressed in the F2 generation in the ratio of ¾ dominant to ¼ recessive. This characteristic 3:1 segregation is referred to as the Mendelian ratio for a monohybrid cross.
Principle of Segregation
plants crossed did not produce progeny of intermediate appearance
These alternative traits were expressed in the F2 generation in the ratio of ¾ dominant to ¼ recessive. This characteristic 3:1 segregation is referred to as the _______________ for a monohybrid cross.
Mendelian ratio
Modern day description of Mendel’s findings:
Parents pass their physiological traits to their offspring via ____________ , individual receives _____copy of each _______ from each parent
genes
one
gene
Modern day description of Mendel’s findings:
Not all copies of a gene are___________
The alternative forms of a gene are called_________
When two haploid gametes containing the same allele fuse during fertilization, the resulting offspring is said to be _____________
When the two haploid gametes contain different alleles, the resulting offspring is said to be __________
identical
alleles
homozygous
heterozygous
Modern day description of Mendel’s findings:
The two alleles remain discrete—they neither _____ with nor _____ each other. Therefore, when the individual matures and produces its own gametes, the alleles ________________________
blend; alter
segregate randomly into these gametes (offspring)
Modern day description of Mendel’s findings:
In all individuals, only ____ allele is expressed
dominant) and the other is unexpressed (recessive
one
Modern day description of Mendel’s findings:
The total set of alleles that an individual contains is called ______________
The physical appearance or other observable characteristics of that individual, which result from an allele’s expression, is termed _______________
the _________ is the blueprint, and the _________ is the visible outcome in an individual.
genotype
phenotype
genotype
phenotype
What process is this?
Alternative alleles for a character segregate from each other during gamete formation and remain distinct
Principle of Segregation
Mendel’s first law of heredity
Principle of Segregation
What process is this?
The two alleles for a gene segregate during gamete formation and are rejoined at random, one from each parent, during fertilization.
Principle of Segregation
The physical basis for allele segregation is the behavior of ___________ during ________. Homologues for each chromosome disjoin during _________ of ________. The second meiotic division then produces _________ that contain only _____ homologue for each chromosome.
chromosomes
meiosis
anaphase 1; meiosis
gametes
one
Mendelian ratio of 3:1 is actually a ratio of ___________
1:2:1
1 Homozygous dominant : 2 heterozygous : 1 homozygous recessive
allows symbolic analysis
Punnett square
allows simplistic calculation and representation of crosses
Punnett square
IN a punnet square the UPPER CASE LETTER represents ________
LOWER CASE LETTER REPRESENTS _________
dominant trait
recessive trait
Genotype of a true-breeding purple-flowered individual would be designated _______.
Genotype of an individual that is true-breeding for the recessive white-flowered trait would be designated ____
PP
pp
Those that _____________ possess dominant traits would have one or two capital letters (PP or Pp)
phenotypically
____________, dominant
traits are expressed as homozygous dominant (PP) or heterozygous (Pp)
Genotypically
________________ are genotypically homozygous
recessive (pp) and phenotypically exhibit the recessive trait
recessive traits
We use __________ to visually calculate the probability of offspring having a specific genotype or phenotype
Data from experiments vs.
Calculated heredity
Punnett squares
White-flowered parent (pp) can produce only ________
True-breeding purple-flowered parent (PP, homozygous dominant) can produce only________
The union of these gametes can produce only _____________ offspring in the F1 generation
The phenotypic ratio is 3 purple: 1 white. The genotypic ratio is _____________
p gametes
P gametes
heterozygous Pp
1PP:2Pp:1pp.
2 probability rules help predict monohybrid cross results : these rules include
___________________, ___________________
- Two events are mutually exclusive if both cannot happen at the same time.
- The event is independent
a breeding experiment between P generation (parental generation) organisms that differ in a single given trait. The P generation organisms are homozygous for the given trait, however each parent possesses different alleles for that particular trait.
Round Rr) vs Wrinkled (Rr)
monohybrid cross
Round Rr) vs Wrinkled (Rr) is an example of what experiment?
monohybrid cross
What are the possible combinations of alleles?
RR: 1/4
Rr: 1/2
Rr: 1/4
states that the probability of two independent events both occurring is the product of their individual probabilities.
rule of multiplication
Consider the purple F1 parents. They are all Pp (heterozygotes), so the probability that a particular F2 individual will be pp (homozygous recessive) is the probability of receiving a p gamete from the male (½) times the probability of receiving a p gamete from the female (½), or ¼:
What rule is this?
The probability of receiving a p gamete from the male (½) X the probability of receiving a p gamete from the female (½) = ¼:
rule of multiplication
Mom: ½ X Dad: ½ = (For genotype) RR: ¼
What rule is this?
To apply this to our cross of heterozygous purple F1, FOUR mutually exclusive outcomes are possible: PP, Pp, pP, and pp. The probability of being heterozygous is the same as the probability of being either Pp or pP, or ¼ plus ¼, or ½:
The rule of addition
Mom: ½ X Dad: ½ = (For genotype) Rr: ¼ + ¼ = 2/4 = ½
The probability of either of two different numbers is the sum of the individual probabilities, or restated as the
The rule of addition
T/F
Humans possess several dominant and recessive traits
Genetics studies crosses already performed or, ___________ history
true
family
A consistent graphical representation of matings and offspring over multiple generations for a particular trait.
Used by genetics
pedigree
A pedigree can form _____________________
models of inheritance
A dominant pedigree, traced the inheritance of a form of blindness caused by a dominant allele called
Juvenile glaucoma
A form of an allele causes this disease in children that eventually leads to blindness
Juvenile glaucoma
What disease was this?
Pedigree of all matings determined the
original carrier of the allele who died in 1495, France
Since the trait shows up frequently in every generation, geneticists deduced this allele is the dominant form
Juvenile glaucoma
Follows the behavior of two different traits in a single cross
dihybrid cross
A single genetic cross involving two different traits, such as flower color and plant height.
dihybrid cross
Mendels next question was?
Do different traits behave independently in hybrids
Mendels next question: Do different traits behave independently in hybrids
What is the name of this experiment?
First established a series of true-breeding lines of peas that differed in two of the seven characters he had studied
He then crossed contrasting pairs of the true-breeding lines to create heterozygotes. These heterozygotes are now doubly heterozygous, or dihybrid
Finally, he self-crossed the dihybrid F1 plants to produce an F2 generation, and counted all progeny types.
Mendel’s dihybrid cross in pea plants
– Example cross:
• Pea shape: Round (R) or wrinkled (r)
• Pea color: Yellow (Y) or green (y)
• The dihybrid cross between two true-breeding plants:
– Dominant: Round (RR) and Yellow (YY)
– Recessive: Wrinkled (rr) and green (yy)
If all genes act independently, then there can only be four possible phenotypic combinations
- Round Yellow (RRYY, RrYy)
- Round Green (RRyy, Rryy)
- Wrinkled Yellow (rrYy, rrYY)
- Wrinkled Green (rryy)
What did Mendel actually observe? From a total of 556 seeds from self-fertilized dihybrid plants, he observed the following results:
315 round yellow (signified R____ Y____, where the underscore indicates the presence of either allele),
108 round green (R____ yy),
101 wrinkled yellow (rr Y____), and
32 wrinkled green (rr yy).
These results are very close to a 9:3:3:1 ratio. (The expected 9:3:3:1 ratio for 556 offspring is 313:104:104:35.)
Mendel’s second law of heredity
Principle of Independent Assortment
What law is this?
In a dihybrid cross, the alleles of each gene assort
independently
Principle of Independent Assortment
What law is this?
The segregation of different allele pairs is independent
Principle of Independent Assortment
In a ___________, an individual with unknown genotype is crossed with the homozygous recessive genotype—that is, the recessive parental variety.
testcross
How did Mendel continue to test his hypothesis and model?
testcross
To test his model further, Mendel devised a simple and powerful procedure called the
testcross
Crosses the unknown with a known and determines ratios of offspring
testcross
Example cross: Purple (PP or Pp) and White (pp) flowers
Cross unknown with ______
If cross results in any ________ flowered offspring, then that suggests unknown parent is__________
White (pp)
white
heterozygous
Mendel used test-crosses to determine
the genotype of his F2 generation plants
used to determine the genotype of an individual when two genes are involved
testcrosses
Describes a mode of inheritance in which more than one gene affects a trait, such as height in human beings; polygenic inheritance may produce a continuous range of phenotypic values, rather than discrete either–or values.
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polygenic inheritance
What is this describing?
More than one gene is involved in producing a trait.
Produces traits that have a continuous range rather than two independent values.
Ex: Height in pea plant vs height in humans
polygenic inheritance
Most __________ have contributions from
several _______, resulting in the range
phenotypes
genes
Variation in a trait that occurs along a continuum, such as the trait of height in human beings; often occurs when a trait is determined by more than one gene.
continuous variation
A trait that is determined by the effects of more than one gene; such a trait usually exhibits continuous variation rather than discrete either–or values.
quantitative traits
An allele that has more than one effect on phenotype is said to be
pleiotropic
when a single gene affects more than one trait
Pleiotropy
Some genes have more than two_______________
alleles
How many alleles does blood have?
3
A,O,B
Describes a case in which two or more alleles of a gene do not display clear dominance. The phenotype of a heterozygote is intermediate between the homozygous forms. For example, crossing red-flowered with white-flowered four o’clocks yields pink heterozygotes.
incomplete dominance
In __________________, the phenotype of the heterozygote is intermediate between the two homozygotes.
incomplete dominance
Cross between Rr x Rr results
incomplete dominance
Describes a case in which two or more alleles of a gene are each dominant to other alleles but not to each other. The phenotype of a heterozygote for codominant alleles exhibit characteristics of each of the homozygous forms. For example, in human blood types, a cross between an AA individual and a BB individual yields AB individuals.
codominance
neither allele is recessive and exhibits phenotype of both traits
codominance
The gene that determines ABO blood types encodes an enzyme that adds
The gene that determines ABO blood types encodes an enzyme that adds
The gene that encodes the enzyme, designated ___, has three common alleles: __, whose product adds galactosamine; ___, whose product adds galactose; and ____, which codes for a protein that does not add a sugar.
I
IA
IB
i
IA and IB alleles are ________________
codominant (dominant over the i)
IA and IB alleles lead to sugar addition, whereas the i allele does not.
i is recessive (O-blood type)
_____ and _____ alleles lead to sugar addition, whereas the i allele does not.
IA; IB
Type A individuals add only galactosamine
IAIA homozygotes or IAi heterozygotes (two genotypes).
Recieve A and O
Donatae A and AB
IAIA homozygotes or IAi heterozygotes (two genotypes).
Type B individuals add only galactose
IBIB homozygotes or IBi heterozygotes (two genotypes).
IBIB homozygotes or IBi heterozygotes (two genotypes).
Receive _____ and ______, Donates to ______ and ______
B
O
B
AB
Type AB individuals add both sugars and are
IAIB heterozygotes (one genotype).
Universal reciever, donates too _____
AB
Type O individuals add neither sugar and are
ii homozygotes (one genotype).
Universal donor, recieves ____
O
The type of sugar attached to RBCs is dependent on the________________
allele that is expressed
Sugar molecules are specific to an individual’s ________ system; recognizes ______
Immune
RBCs
