Bio 110 > exam block 3: GENETICS! > Flashcards

exam block 3: GENETICS! Flashcards

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1
Q

morphology

A

physical appearance

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2
Q

P-generation

A

parental generation

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3
Q

F1 generation

A

result of crossing two parents (p generation)

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4
Q

F2 generation

A

result of self-polinated F1 generation hybrids

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5
Q

A diploid individual always has ___ gene(s) for every trait.

A

2

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6
Q

Gametes of diploid individuals have ___ gene(s) for every trait.

A

1

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7
Q

Genotype

A

an organism’s genetic makeup for a particular trait.

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8
Q

Phenotype

A

the trait produced by the alleles an individual has.

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9
Q

How do enzymes play a role in phenotype expression?

A

The different alleles at a gene differ in their DNA sequences, thereby producing different enzymes when transcribed into RNA and translated into a protein.

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10
Q

Dominant alleles

A

alleles that are fully expressed in the phenotype of a heterozygote.

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11
Q

Recessive alleles

A

alleles whose phenotypes are not expressed in a heterozygote

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12
Q

mendelian traits

A

traits with simple dominant/recessive expression patterns where one trait is completely dominant over the other.

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13
Q

monohybrid cross

A

crossing individuals to examine a single character in their offspring.

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14
Q

punnet square

A

tool for predicting the genotypes and phenotypes of offspring in a genetic cross involving a mendelian trait.

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15
Q

test cross

A

used to determine whether an individual with a dominant phenotype is heterozygous or homozygous dominant for the trait.

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16
Q

mendel’s law of segregation

A

refers to the separation of homollogous chromosomes into different gametes. By the end of meiosis, each haploid gamete contains one copy of each type of chromosome, and thus one copy of each gene found on those chromosomes.

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17
Q

Mendel’s law of independent assortment

A

explains how meiosis creates the different types of gametes used in a dihybrid cross.

To calculate the number of different chromosome combinations produced by independent 2^n (n is the number of homologous pairs, aka the haploid number)

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18
Q

Dihybrid cross

A

a cross following the inheritance of two traits.

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19
Q

How to set up a dihybrid cross

A

FOIL each of the parental genotypes and put the results on the top and sides of the 4x4 punnet square.

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20
Q

What is the difference between mendel’s law of segregation and mendel’s law of independent assortment?

A
  • Mendel’s law of segregation refers to when alleles on homologous chromosomes separate in meiosis I.
  • Mendel’s law of independent assortment is the concept that if the genes for different characteristics reside on different chromosomes, they will assort independently during metaphase I, which causes many different gamate combinations to be possible.
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21
Q

why does it make sense that each chromosome has many gene?

A

complex organisms (like humans) have huge numbers of genes to govern their biocheical processes, and yet, the number of chromosomes in these organisms is often small.

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22
Q

The rule of multiplication (probability)

A
  • allows one to calculate the probability of two or more independent events occurring together in a specific combination.
  • calls for the multiplication of the probabilities of the two independent events that must occur to get the desired outcome.
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23
Q

Pedigrees

A
  • describe the interrelationships between parents and children, over generations, regarding a specific trait.
  • half filled symbols on a pedigree denote carriers (heterozygotes).
  • completely filled symbols denote the expression of the trait
  • empty symbols denote individuals who do not express the trait.
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24
Q

carriers

A

organisms that have inherited a recessive allele for a trait but don’t express the trait or show symptom of the disease because of the presence of the dominant allele.

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25
Recessive patterns of inheritance
- may skip a generation phenotypically, but there are still carriers present - carriers are only present when two traits have a complete dominance relationship, meaning that one is completely dominant over the other.
26
What are some autosomal recessive diseases?
- cystic fibrosis - sickle-cell disease - phenylketonuria
27
What genotype must phenotypically normal parents of a child with an autosomal recessive disease be?
Heterozygous/carriers
28
Each time two carriers concieve a child, there is a ___% chance the child will exhibit the phenotype, a ___% chance the child will be a carrier, and a ___% chance the child will be a non-carrier.
25, 50, 25
29
cystic fibrosis
- the harmful allele encodes for a protein that is involved in chloride ion transport; as a result, individuals with both harmful alleles (rr) for this gene have problems with salt balance in cells that line the lungs and intestines. this salt imbalance causes the mucus coating of certain cells to become unusually thick, causing affected individuals to show a dangerous buildup of mucus.
30
Phenylketonuria (PKU)
- main symptom is mental retardation - the deffective allele encodes for a nonfunctional phenylalanine hydrolase enzyme that normally converts the amino acid phenylalanine to the amino acid tyrosine. - this causes high levels of phenylalanine, which affects neuronal development which leads to mental retardation. - symptoms can be prevented with proper nutrition that includes a low-protein diet.
31
sickle-cell disease
- most common genetic disease that affects mainly people of african ancestry - affects the hemoglobin molecule found in red blood cells, which is involved in oxygen transport. - the high prevelance of the allele in the population suggests that there is some benefit to carrying it in a heterozygous state.
32
heterozygote advantage
describes the situation in which the heterozygote has a higher relative fitness than either the homozygous recessive or homozygous dominant genotype. best example is sickle-cell disease: individuals who carry the allele are less susceptible to malaria, which is a big problem in africa.
33
dominant patterns of inheritance
- the trait does not skip a generation - where one parent is affected, about half of the offspring are affected.
34
Huntington's disease (HD)
- autosomal dominant disease - causes progressive damage to the nervous system - develops subtly in a person's 30s/40s - characterized by difficulties in three areas: uncontrollable movements, dementia, and psychiatric disturbances
35
most people affected by huntington's disease have: ______________________________.
one deleterious allele and one normal allele (Rr).
36
why is huntington's disease so prevalent?
the disease doesn't become noticeable until after the normal child-bearing age, at which point the child has already inherited the disease.
37
What are the three types of dominance relationships?
- complete dominance - co-dominance - incomplete dominance
38
complete dominance
one allele is completely dominant over the other; this causes offspring to always exhibit only one of the two possible phenotypes
39
incomplete dominance
- individuals who are heterozygous exhibit a phenotype that is intermediate: in between the two homozygous phenotypes. - In the example of flower color, the character (color) is represented by the base letter C, and the alleles encoding that trait (white or red) are listed as uppercase in the subscripts (C^W and C^R).
40
co-dominance
both alleles are expressed in the phenotype of individuals who are heterozygous.
41
multiple alleles
(look at terms for definition)
42
Pleiotropy
when one gene can have multiple affects. example is albanism, in which skin color and hair color are both affected by the same gene.
43
epistasis
refers to when one gene can affect the expression of another gene.
44
polygenic inheritance
occurs when one characteristic is controlled by two or more genes.
45
quantitative character
a phenotype that depends on the combined actions of many genes and the environment. Quantitative characters usually indicate that tha character is controlled by more than one gene (polygenic inheritance).
46
wild type vs mutant phenotype
the phenotype that is prevalent in natural populations is the wild type. More common. Any allele other than the wild type is a mutant phenotype. Less common There could me more than one mutant types in a population but there is only one wild type.
47
sex chromosomes
Refers to the X and Y chromosomes; determines the sex of an individual.
48
sex-linked genes
genes that are located on sex chromosomes.
49
autosomes
all other chromosomes in a cell other than the sex chromosomes.
50
X-Y system
the system of sex determination in humans. - females have two X chromosomes - males have one X chromosome and one Y chromosome
51
hemizygous
term for discussing the genotype of a male for sex-linked genes. - since males only have one chromosomal location for sex-linked genes, the terms homozygous and heterozygous have little meaning.
52
X-O system
System of sex determination for some insects; in this system, females have two copies of the X chromosome (XX) and males only have one (XO). Therefore, the sex of the offspring is determined by whether or not the sperm carries an X chromosome or not.
53
Z-W system
system of sex determination for some birds, insects, and fish. In this systems, the egg cells can wither have a Z chromosome or a W chromosome. Sperm cells always contribute a Z chromosome, so the female gamete determines the sex of the offspring.
54
haplo-diploid system
system of sex determination in bees and ants. Females develop from fertilized eggs and are diploid, whereas males develop from unfertilized eggs and are haploid.
55
color blindness
- trait in which affected individuals are not able to distinguish certain colors. - the genes for both red and green colorblindness are X-linked mutations and the mutations are recessive. Therefore, colorblindness affects more males than females.
56
Hemophilia
- trait in which individuals lack a protein involved in blood clotting, so they can bleed profusely from even a minor abrasion.
57
Barr Body
An inactivated X chromosome that stays condensed throughout the cell cycle. By inactivated, it is meant that most of the genes on the chromosome are not expressed and cannot make proteins. Therefore, both males and females only have one functioning X chromosome.
58
XIST gene
- A gene that is located on the X chromosome responsible for the inactivation of the X chromosome. - Does not code for a protein - one of the few genes expressed on the inactivated X chromosome
59
Genetic map
a map that shows the location of genes on a chromosome.
60
recombination frequency
the frequency of crossing-over between two locations on a chromosome.
61
linked genes
genes that are located on the same chromosome that tend to be inherited together. - the DNA sequence containing the genes is passed along as a unit during meiosis unless they are separated by crossing over.
62
The closer together two genes are located on a particular chromosome the (higher/lower) the probability that they will be inherited as a unit.
Higher
63
complete linkage
genes that are close enough together on a chromosome that they never recombine and are inherited as a unit.
64
how can you use recombination frequencies to determine the distances between genes on a chromosome?
The farther apart two genes are on a chromosome, the higher the recombination frequency.
65
linkage maps
portray the sequence of genes along a chromosome, but do not give the precise location of the genes.
66
map units
used to express the distance between genes. - one map unit is equivalent to a 1% recombination frequency.
67
genes that demonstrate complete linkage have a map distance of ___.
0
68
how do you determine the distance between two genes (in map units)?
divide the number of gamates with recombinant chromosomes by the total number of gamates observed.
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