Chapter 10/15 Flashcards
(78 cards)
1
Q
Classical Genetics
A
Based on how descriptive factors are passed from one generation to the next
2
Q
Triploid (3n) watermelons are produced by crossing a tetraploid (4n) watermelon with a diploid (2n) plant. Explain why this mating produces a 3n individual. Why can mitosis proceed in this individual but meiosis cannot? Why would we want 3n watermelons?
A
Mitosis proceeds this because there are not enough chromosomes to make a tetrate
3
Q
Who is called the father of the science of genetics?
A
Gregor Mendel
4
Q
What can highlight the power of selective breeding?
A
Crop plants & Dog breeds
5
Q
The key to genetics as a science:
1) Predictive:
2) Mathematical:
A
1) Predictive: allows the making and testing of hypotheses
2) Mathematical: analysis of the data, set Mendel apart from people like Darwin and stone age farmers
6
Q
What did Mendel do?
A
He identified heritable traits
- Looked at plant characters
- Noticed the different visible traits pea plants exhibited
7
Q
Which phenotypic traits did Mendel identify in his pea varieties?
A
Flower color; purple or white Flower position; axial or terminal Seed color; yellow or green Seed shape; round or wrinkled Pod shape; smooth or constricted Pod color; green or yellow Height; tall or dwarf
8
Q
Why was the garden pea a great experimental organism?
A
- It was easy to cross
- Easy to grow
- Each pea is an independent fertilization event
- Had a number of different characteristics
9
Q
Which part of the cell is the male gamete? female?
A
The Stamen
Ovule & ovary
10
Q
How could Mendel see if the peas would self-cross?
A
1) He could cover them with a small bag, or fertilization could be performed manually using a paint brush or by holding the stamen that was removed with forceps
2) Then wait for the seed to mature, plant them and see what we get
11
Q
What were the results of Mendel’s 1st experiment? He took pollen from pea plants with wrinkled seeds and put it on the stigma of flowers from plants with smooth seeds.
A
All of the resulting (F1 generation) seeds were smooth… Dominant phenotype
12
Q
What happened when the resulting F1 generation was self-crossed? (smooth seeds dominant)
A
The peas were not all smooth
Round: wrinkled
3:1
13
Q
What type of trait is not present in the F1 seeds, but reappeared in the F2 generation?
A
Recessive phenotype
14
Q
Gene
A
A unit of hereditary information
15
Q
Allele
A
A version of a gene
16
Q
Homozygous
A
Both alleles are the same
17
Q
Heterozygous
A
The alleles are different
18
Q
Genotype
A
The genetic make up of a cell
Ex. GgHh
19
Q
Phenotype
A
A visible or measurable trait
Ex. purple
20
Q
Dominant
A
An allele that produces the phenotype in a heterozygous organism
21
Q
Recessive
A
The ‘invisible’ allele in a heterozygous organism
22
Q
Law of Segregation
A
Two copies of a gene separate from each other during transmission from parent to offspring (meiosis)
23
Q
What accounts for variation in inherited characteristics?
A
Alternative versions of genes
24
Q
How many alleles do the offsprings receive from their parents?
A
Parents will each only contribute one allele to their offspring, even tho they carry two.
- thus, the egg and sperm each only carry one copy of the gene (haploid)
- They unite to give a diploid (2n) zygote
25
Genes are located on __________ at specific locations called ________
Genes are located on chromosomes at specific locations called Loci
26
Genes alternative forms is called ________
- If they are both the same, the genotype is called _____
- If they are different, the genotype is called ___________
Genes alternative forms is called Allele
- If they are both the same, the genotype is called Homozygous
- If they are different, the genotype is called Heterozygous
27
- A heterozygous expressed allele is called _______
| - A heterozygous unexpressed allele is called _______
- A heterozygous expressed allele is called dominant
| - A heterozygous unexpressed allele is called recessive
28
What is the examination of one character?
A monohybrid cross
29
In a monohybrid cross of between a purple flower and a white flower:
- What will the F1 generation be?
- What will the F2 generation be?
```
F1 = all plants will have purple flowers (dominant); they will be heterozygous
F2 = 3/4 will be purple (dominant); 1/4 will be white(recessive)
```
30
Whether an allele is dominant or recessive depends on:
a) how common the allele is, relative to other alleles
b) whether it is inherited from the mother or father
c) Which chromosome it is on
d) Whether it or another allele determines the phenotype when both are present
e) Whether or not it is linked to other genes
d) Whether it or another allele determines the phenotype when both are present
31
Genotypic annotation
- Alleles are represented by single letters
| - Dominant alleles are represented by capital letters
32
What is the chance of an specific allele being passed on? EX. from Tt
50% chance of either allele being passed on
- 1/2 of gametes will carry the T allele
- 1/2 will carry the t allele
33
Law of independent assortment
Alleles of different genes will assort independently of each other during meiosis
*unless the genes are near each other on the same chromosome*
34
- In the monohybrid cross ___ of the F2 have the dominant phenotype
- In the dihybrid cross ______ of the F2 have the double dominant phenotype
- In the monohybrid cross 3/4 of the F2 have the dominant phenotype
- In the dihybrid cross 3/4 X 3/4 (9/16) of the F2 have the double dominant phenotype
35
Trihybrid cross
Will compare 3 traits
| Ex. flower color, position, seed color
36
If the seed of the F1 generation were planted and self-crossed, what is the probability that in a pod with 4 seeds, 2 are yellow and 2 are green?
*Gg x Gg cross*
Gg x Gg - probability of green seeds = 3/4
Gg x Gg - probability of yellow seeds = 1/4
So the probability that you would get 2 green and 2 yellow seeds would be:
3/4 x 3/4 x 1/4 x 1/4 = 9/256
37
If there are 6 different ways in which the 4 peas could be place in the pod, what is the probabilities together?
**So the probability that you would get 2 green and 2 yellow seeds would be:
3/4 x 3/4 x 1/4 x 1/4 = 9/256**
(9/256)*6 = 54/256
| The probability =0.21
38
How are Mendel's experiments different?
- Quantified - fractions, math
- Followed generations
- Picked easily distinguishable traits
39
How can we have many different alleles in a population despite the fact that any given individual can only have two alleles?
- 1 person can only have 2 alleles for a particular gene
| - the human population has 1000s of different allleles on different genes
40
Test Crosses
Test crosses are done by crossing the unknown dominant with a recessive... which allows us to determine the genotype of the unknown
41
Test Crosses:
1) What will happen if the unknown is homozygous dominant?
2) What will happen if the unknown is heterozygous?
1) 100% chance of passing on the allele; the offsprings will all express the dominant trait
2) 50% chance of passing on the allele; 1/2 of the offsprings will express the dominant trait
42
Pedigree Analysis
Examining the pattern of inheritance of a characteristic we can then make predictions about the trait
- Also used to search for the genetic markers of disease
43
What can inheritance patterns tell us?
The dominance/ recessiveness of a trait
44
Cystic fibrosis
A disease that causes mucus accumulation in your lungs
45
What triggers the development of maleness?
A gene calle SRY on the Y chromosome
| - Even for those who have an extra X chromosome
46
What is the sex determination in most insects?
There is a dose response relationship
- X = male
- XX = female
47
What is the sex determination in fruit flies?
There is still a dose response relationship
- XY = male
- XX = female
48
What is the sex determination in bees?
They use a haplo-diploid system to determine sex
- males = haploid
- females = diploid
49
How is the sex determined for birds?
For birds, sex is determined by the egg rather than the sperm
- Female = W
- Male = ZZ
50
What did Morgan find in his fruit fly collection? What did he do to pass it on?
- He found a fruit fly with white eyes
| - He crossed it with other flies and found that the white phenotype could be passed on but it had an odd segregation
51
Morgan could never find females with white eyes, therefore he developed the hypothesis that?
Morgan hypothesized that the white eye phenotype was due to a defect on the sex determining chromosome (recessive trait)
52
What did Hunt conclude?
The white eye color was 'linked' to sex determination because the gene was on the X chromosome
53
Incomplete dominance
Sometimes a heterozygous offspring will be intermediate in the phenotype
54
Most phenotypes are the result of ________, the ______ is made from ______ transcribed off the ______________
Most phenotypes are the result of protein function, the protein is made from mRNA transcribed off the chromosomal DNA
55
What happens if a gene copy cannot make enough mRNA?
Then not enough protein is made
56
What type of disease is Hypercholesterolemia?
It is an example of an incomplete dominance human disease
57
If an interbreeding population of snapdragons are red, pink, and white, why are testcrosses redundant?
Because by looking at the color we can tell what they are
| Pink= heterozygous
58
Many genes have more than two alleles, and sometimes they are both expressed.. When?
Human blood type
| O, A, B, AB
59
What can Blood types be used for?
Blood types can be used in forensic investigations or as a test of paternity of a child
60
Which antibodies are present in each blood type?
1) O
2) A
3) B
4) AB
1) O = Anti-A; Anti-B
2) A = Anti-B
3) B = Anti-A
4) AB= none
61
What are the possible genotypes for each blood type?
1) O
2) A
3) B
4) AB
1) O = ii
2) A = (I^A) (I^A) or (I^A)i
3) B = (l^B) (l^B) or (I^B)i
4) AB= (I^A)(I^B)
62
Maria has type O blood and her sister has type AB
a) What are the possible genotypes of the girls parents?
b) If the girls know that their maternal grandparents had type A blood, how can we refine our answers in part a?
Maria = ii Sister = (I^A)(I^B)
a) P1= (I^A)i P2 = (I^B)i
b) maternalGP= (I^A)(I^A) or (I^A)i
Therefore the mother has the genotype (I^A)i, and the father has the genotype (I^B)i
63
Epistasis
A phenomenon in which the expression of one gene depends on the presence of one or more 'modifier genes'
64
Why might more then one gene be required? (1)
| Brown & White
1) Enzymes required for brown eye color might be made up of 2 proteins (quaternary structure)
- Protein from gene A & a protein from gene B
* *In this case the organism would need a functional copy of each gene (dominant) to produce brown eyes- AABB or AaBb
- Crossing AaBbxAaBb = 9:7 ratio
65
Why might more then one gene be required? (2)
| Brown & White
2) Two enzymes are required for brown eye color (biosynthetic pathway)
(white) --(protein from gene A)-->(white)--protein from gene B)-->(brown)
* In this case, the phenotypic analysis would also be 9:7
66
What if the intermediate in our biosynthetic pathway was blue?
(white)--(protein from gene A)-->(blue)--protein from gene B)-->(brown)
The ratio would be Brown:Blue:White = 9:3:4
67
Quaternary structure
The arrangement of multiple folded protein or coiling protein molecules in a multi-subunit complex.
68
Biosynthetic pathway
The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life
69
Gene Linkage
When the gene loci is on the same chromosome
| - This blocks independent segregation
70
Loci
The specific location of a gene or DNA sequence or position on a chromosome
71
A gene for body color & wing shape are on the same chromosome:
If they were crossed, what would the F1 phenotypic ratio be?
F1 phenotype = all gray body & straight wings
| F1 phenotype = b+bc+c
72
A gene for body color & wing shape are on the same chromosome:
If they were crossed, what would the F2 phenotypic ratio be?
We would do a testcross F1=b+bc+c with bbcc(homozygous recessive)
Nonrecombinants = b+bc+c & bbcc
Recombinants = b+bcc & bbc+c
73
How can we determine how far apart the gene loci are on the chromosome?
We can use the frequency of crossing over to determine how far apart they are on the chromosome
- Centimorgans are the units of distance
74
Remember that __________ and ________ have _____ it also encodes genes which must be passed on from generation to generation
Remember that mitochondria and chloroplasts have DNA it also encodes genes which must be passed on from generation to generation
75
In mammals, where are the mitochondrial chromosomes passed through?
They are passed through the maternal line
76
Sperm cells lose their mitochondria during________
Fertilization
77
In mammals, there are only about ___ genes that encode proteins required for _________________
- If alleles of these genes are defective, then ____________ result
In mammals, there are only about 13 genes that encode proteins required for cellular respiration
- If alleles of these genes are defective, then specific diseases result
78
What do mitochondrial diseases often have?
Because of mitochondria's job is to supply energy, mitochondrial diseases often have muscular symptoms
- We can track the phenotypes due to mitochondrial diseases in pedigrees
