Exam #4 - Genetics Flashcards
Is blending a correct model of inheritance?
No
Why did Gregor Mendel study pea plants?
1) Peas are eukaryotes
2) Cheap and easy to handle
3) Within a short amount of time, you can generate the next generation. Within a year or less
A character = ?
A characteristic
Flower color is a ________?
The plant height is a ________?
The pea color is a _________?
The pod shape is a __________?
Characteristic. These are all TRAITS
Variety is a TYPE of _________.
character
Red flowers….white flowers…tall height…small height…yellow peas…green peas…these are ________.
varieties. (Varieties are more SPECIFIC)
- **Trait: Flower Color
- **Variety: Red Flower (MORE SPECIFIC = VARIETY)
T/F: A pea plant can fertilize itself
True
In nature: self pollinate
Mendel: ____ _______
cross pollinate
Start with a parent that produces offspring just like itself…this is called _____ _______.
true breeding
Start with true breeding, but take two _______ true breeding varieties and _____ them. See what you get!
different, cross
This was Mendel’s experiment:
Take a true breeding parent of one ______, and cross it with a true breeding individual of another ______. Same characteristic, but two different _______. And that will produce an offspring.
variety
Since this offspring is a parent of two varieties, it is known as a ______.
hybrid.
A hybrid generate by cross pollination
The hybrid is then allowed to ____ ________.
This last group of offspring is analyzed to see what conclusion we can draw.
self pollinate
The original generation is called _.
The hybrids are called __.
The final set of offspring is called __.
P
F1
F2
Mendel’s experiment #1:
Crossed a true breeding individual with ______ seeds with a true breeding individual with _______ seeds.
round, wrinkled
What are the offspring? (F1)
All round
What were the results of the final offspring? (F2)
Round, wrinkled. 3:1 ratio
Wrinkled came back…
What conclusions did he draw from experiment #1?
1) His observations contradicted the blending model
2) Characters/traits are produced by ‘heritable factors’ that are DISCRETE
**Today we know that ‘heritable factors’ = genes
Experiment #1 conclusions:
1) Characters/traits are produced by ‘heritable factors’ that are DISCRETE
2) An organism has ___ genes for each trait.
- ___ from each parent
Today we know:
We inherit a pair of ________ _________
-They have the _____ GENES!
two
one
homologous chromosomes
SAME
Why different phenotypes for a trait?
A gene has different “versions” or alleles (round, wrinkled)
Experiment #1 conclusions:
1) Characters/traits are produced by ‘heritable factors’ that are DISCRETE
2) An organism has TWO genes for each trait.
3) Genes have alternate versions called _______.
Today we know:
A gene can vary in its ________ ________.
alleles
nucleotide sequence
Based on mender’s experiment…
Round seed phenotype: _________
Wrinkled seed phenotype: _________
DOMINANT
Recessive
Experiment #1 conclusions:
1) Characters/traits are produced by ‘heritable factors’ that are DISCRETE
2) An organism has TWO genes for each trait.
3) Genes have alternate versions called ALLELES
4) When different alleles are TOGETHER:
- Dominant allele: affects ________.
- Recessive allele: DOES NOT affect ________.
appearance
Experiment #1 conclusions:
1) Characters/traits are produced by ‘heritable factors’ that are DISCRETE
2) An organism has TWO genes for each trait.
3) Genes have alternate versions called ALLELES
4) Dominant allele: affects appearance
5) Alleles separate during gamete production.
- This is called ____ __ _________.
Today we know:
_______ __________ separate during meiosis I
Law of segregation
homologous chromosomes
Particulate Model of Inheritance:
‘Genetic material’ is composed of UNITS which are passed on to offspring, and which retain their ________.
IDENTITIES
Why 3:1 in F2?
USE A PUNNET SQUARE!
Punnet Square: predicts the result of a cross by accounting for _______ fertilization.
random
______ is the process of change in the genetic code.
mutation
Every allele today came about by _______.
mutations
_______ is the physical appearance of an organism.
phenotype
The genes that you have, or genetic makeup, is called _______.
genotype
Your _______ is what gives you your ________.
genotype, phenotype
The ________ of the parents are purple flower and white flowered plants
phenotypes
The ________ is two dominant alleles, two purple alleles, two recessive alleles.
genotype
If you have two of the same allele, you are said to be _________.
homozygous
If you have two different alleles, you are said to be ________.
heterozygous
A true breeding individual is _________.
homozygous
The F1 is _________.
heterozygous
Among the F2, we have some _________ and some ________.
heterozygotes and heterozygotes
A ________ ratio means the ratio of different genotypes.
genotypic
How many different genotypes were in the purple, white flower cross?
3
Homozygous dominant
Heterozygous
Homozygous recessive
Present at a 1:2:1 ratio
When the parents differ in one trait, it’s called a ________ cross.
monohybrid cross
ex: Pea shape: round and wrinkled
when the parents differ in two traits, it’s called a _________ cross.
dihybrid cross
ex: Flower color and Pea shape
Breeding an organism of unknown genotype with a recessive homozygote is called a ________, because it can reveal the genotype of that organism.
testcross
Mendel’s Experiment #2
Follow _____ and _____ traits
shape and color
Hypothesis #1: the genes are physically ________.
connected
When the F1 generation goes to make offspring, what must occur?
Law of segregation
Hypothesis #2: The genes are ___ physically connected.
not
The conclusion was that…
Pea color and pea shape are NOT connected
A pair of alleles (pea color) MAY sort to gametes independently of other pairs of alleles (pea shape). This is known as…?
Law of independent assortment
A pair of alleles (pea color) MAY sort to gametes independently of other pairs of alleles (pea shape). This is known as the LAW OF INDEPENDENT ASSORTMENT
Today we know: Each pair of homologous chromosomes sorts randomly during ________ _.
meiosis I
Will the law of independent assortment apply to any two pairs of alleles?
Only if the gene is on different chromosomes
Pea color and pea shape are on different chromosomes
If the genes are on the same chromosome, what doesn’t apply?
Law of independent assortment
If two different genes are on different chromosomes, they will sort independently of each other and will allow for the law of independent assortment.
If two different genes are on the same chromosome, then it will not sort independently. They will sort together because they’re physically ________.
connected
Why is it that the dominant allele affects the phenotype?
The recessive allele is not producing a functional _______.
protein.
The dominant allele produces a functional protein, which is why we see the dominant allele, as opposed to the recessive allele, which produces an ineffective _______.
protein
The recessive phenotype is not caused because you have recessive alleles, it’s because you DON’T HAVE…..?
Dominant alleles
If the heterozygote looks in between the two dominant phenotypes, then we say the dominance is ________.
Ex: Pink flower has C^r (red color) and C^w (white color)
incomplete
When a heterozygote shows intermediate phenotype in between the two homozygous individuals, it’s called _______ ________.
incomplete dominance.
The flower is pink instead of red or white
Mendel discovered ______.
genes
Mendel identified that characters are identified by _____.
genes
If you have two alleles, only ___ will be placed in the egg and ___ will be placed in the egg.
one
Only one will get placed into the sperm, and only one will be given to your offspring. This is because the cell division that produces your gametes, the meiosis separates the gene pair, specifically meiosis I. That is called…?
Law of segregation - only give one to your offspring
When homozygous dominant individuals and heterozygous individuals look the same, this is called _______ _________.
complete dominance
When both alleles affect a phenotype, it’s called ________.
codominance
How many different alleles can one person have for a gene?
TWO - one from mom, one from dad
________: a CHANGE in the nucleotide sequence of a gene
Mutation
T/F: A dominant allele is not necessarily most common in the population
TRUE.
Most peas have the genotype: homozygous recessive. So the dominant allele is quite rare in the pea plant population.
So again, there’s NO rule saying the dominant allele is the most common allele.
Some phenotypes result from more than 1 gene. This called…?
Polygenetic inheritance.
3 different GENES give rise to different eye color
Skin color comes about from 6 different GENES.
NOT alleles *GENES!!!!
Each gene has different alleles, now think of the broad range of possible human skin colors
Phenotype is the result of…? (2)
1) Genotype - genes
2) Environment - how much sun you’ve recently gotten
The greatest number of different alleles for a gene that a single person can have is _?
2
Mendel observed traits, NOT __________.
chromosomes
The __________ ______ of ________ says that the genes are located at specific positions on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.
chromosomal theory of inheritance
Thomas Morgan’s experiments
He used _________.
fruit flies
Some of the characters Morgan observed were: (3)
1) eye color
2) body color
3) wing shape
_____ ____ phenotype: typically found in nature, resulting from ‘normal’ allele
wild type
______ phenotype: occurs when a mutation produces a new allele
mutant
Experiment #1 conclusions
1) ___ allele is dominant to the white allele
2) fly eye color is linked to ___
3) fly color gene is ___-linked
red
sex
sex
What’s the first thing a parent does when it goes to make the next generation?
Law of segregation
A gene on a sex chromosome is called …?
Sex linked gene
Which parent, male or female, determines the sex of the offspring?
Male (XX).
What is the ratio of males to females of any cross?
50/50
Who usually shows a recessive phenotype?
MALES.
For X-linked genes, usually it’s the male who shows the recessive phenotype.
A sex linked gene is a gene on the... X-chromosome Y-chromosome Either the X or the Y Both the X and the Y
Either X or the Y
For an X-linked gene, who usually shows the recessive phenotype?
MALES
The ____ method is a way of determining the possible gametes when looking at two different genes: body color and wing shape.
- You take the first allele of each gene
- Then the two outer alleles
- Then the two inner allele
- Then the last two alleles of each gene
FOIL
Experiment #2 conclusions
_________ _________ does NOT apply, because the body color and wing shape genes are linked (they’re on the same chromosome)
Independent assortment
_______ _____: genes located on the same chromosome
linked genes
________ _______ ‘unlinks’ linked joins, and then rejoins them. But not with the same allele, but with the allele with the homologous chromosome.
Crossing over
Genes are recombined in TWO ways:
1) ________ ________:
- -genes on different (non homologous) chromosomes
2) ________ _____:
- -genes on homologous chromosomes
independent assortment
crossing over
The body color and wing shape genes on drosophila are:
1) on the same chromosome
2) on different chromosomes
3) they’re capable of independent assortment
4) they’re sex linked
5) two of these answers
1) on the same chromosome
In the experimental scheme used by Gregor Mendel, the parental generation is ____-_______ to generate the F1 generation.
cross-pollinated
If an allele is recessive, then it…?
only affects the phenotype when the second copy of the gene is recessive
The law of independent assortment applies to the pea plant seed color and seed shape genes because…?
the genes are on different chromosomes
The pea plant seed color exhibits _______ dominance.
complete
An X-linked gene is…?
always found on the X chromosome
