Lecture 2a and b: Chromosomes Flashcards
Simple Mendelian Inheritance involves what gene to allele ratio
1 single gene with 2 different alleles
When studying human traits, it’s not ethical to control parental crosses (like Mendel and pea). Rather we rely on information from…
Pedigrees
Used to determine the pattern of inheritance of traits in humans
Pedigree analysis
For something to be autosomal recessive disease, it must be…
homozygous
Examples of an autosomal recessive disease?
Sickle cell anemia, CF
A minority of human diseases are causes by….
dominant mutations
For something to be a dominant mutation, an affected individual needs to have…
only inherited one copy of the mutant gene from an affected parent
Dominant mutations cause a ___ pattern of inheritance
dominant
Example of an autosomal dominant disease
Huntingtons disease (neurodegenerative disease)
p53 is a ____, if ___ or more units are mutated—the protein doesn’t work
tetramer, 1
Dominant negative mutation example
p53 is a protein that prevents cancer, but in more than 50% of cancers, it is mutated
Most p53 mutations are…
simple loss of function (both copies of gene deleted)
Gain of function mutation example
Ras promotes cell division. Mutated in 20% of cancers and is overactive
The common explanations for dominant disorders are…
- Haploinsufficiency
- Gain of function mutations
- Dominant negative mutations
The heterozygote has 50% of the normal protein in _____. However, you need the total protein to be fine.
Haploinsufficiency
Mutation changes the protein so it gains a new function
gain of function mutation
the altered gene product acts antagonistically to the normal product
dominant negative mutations
Many genetic diseases are inherited as ____, where the mutant genes responsible have been cloned and mapped.
autosomal dominants
Female is the carrier but the male gets the disease
X linked genes
A ____ for an X linked disease shows mostly ___ affected with their mothers as carriers
pedigree, males
Example of an X linked gene
Muscular dystrophy and hemophilia
Traits where one allele is dominant in one sex but recessive in the opposite sex
Sex influenced traits
Sex influence is a phenomenon of
heterozygotes
Most sex influenced traits are….
autosomal
Ex. of sex influenced traits
baldness
Bb and BB mean there will be balding, but bb means there will not. Allele B behaves ___ in males and ___ in females.
dominant, recessive
Pattern baldness results from the expression level of a gene that converts….
testosterone to 5-DHT
Testosterone levels are ___x more in males than females
5
The heterozygous exhibits a phenotype that is intermediate between the corresponding homozygotes.
Incomplete dominance
Example of incomplete dominance
A red homogenous flower and white homogenous flower make a pink heterozygous flower
An allele is dominant in some heterozygous individuals but not in others
Incomplete penetrance
Example of incomplete penetrance
polydactyly
polydactyly is what kind of trait
autosomal dominant (only need one mutant copy)
The measure of penetrance is described at what levek?
population
In incomplete penetrance, if 60% of heterozygotes are carrying a dominant allele exhibit the alleles trait, the trait is ___ penetrant
60%
In most cases with incomplete penetrance, the range of phenotypes is thought to be due to influences of the…
environment and/or genes
Phenomenon where a heterozygote is more vigorous than either of the corresponding homozygote
Overdominance
Sickle cell anemia is what kind of disorder
Autosomal recessive
Ex. of overdominance
Sickle cell anemia. If you are heterozygote you are resistant but if you are homozygote—you get it.
Over dominance is due to, at the molecular level…
to two alleles that produce slightly different proteins
Enviornmental conditions may have a great impact on the ___ of the individual
phenotype
By geneticists examining a range of conditions in regards to environmental conditions, this allows them to see the ____ of the environmental influence on phenotypic range.
norm of reaction
There are multiple alleles that exhibit a…
dominance hierarchy
Coat colors in rabbits is an example of…
4 dif alleles that exhibit dominance hierarchy
Himalayan pattern of coat color in rabbits is an example of a….
temperature sensitive conditional allele
Produced by the immune system that bind to things that are foreign to the body. The binding signals WBC to destroy the foreign thing
Antibody
Something that is recognized by the immune system antibodies
antigen
Example of multiple alleles with co-dominance
ABO blood group (A and B dominant over O)
The ABO blood group is determined by the…
type of antigen present on the surface of RBC
AB blood groups are expressed in a ____ person
heterozygous
O blood group represents a…
loss of function
Determined by the type of carb antigen (sugar) recognized on the surface of….
ABO blood group, RBC
Antigens ___ arises when a sugar is added to a sugar chain already in the surface of the RBC by an enzyme controlled by the allele of the I gene
A and B
Allele i is a __allele that is ___ to both IA and IB in ABO blood group
null, recessive
An allele that has the potential to cause the death of an organism
lethal
Lethal alleles are typically the result of mutations in….
essential genes
Many lethal alleles prevent ____.
cell division
May kill an organism only when certain environmental conditions prevail
conditional lethal alleles
The situation where the alleles of one gene can mask the phenotypic effects of the alleles of another gene
Epistasis
When genes in the same pathway, but one gene comes before the other and masks the effects of the gene after it
epistasis
Plays a role in coat color in rodents, two true breeding parents are crossed and become ____. The F1 ____ is crossed and produces what ratio?
epistasis, agouti animals, 9:3:4
At least one copy of each dominant results in ____ color
agouti
Refers to one gene influencing 2 or more seemingly unrelated phenotypic traits
Pleiotropy
Occurs when both parents express the same, or similar recessive phenotypes but produce offspring with a wild-type phenotype
complementation
Example of complementation
White flowers homozygous (CCpp) and (ccPP) are crossed to make a purple heterozygous flower (CcPp)
Occurs when one gene can compensate for the loss of function of another
Gene redundancy
Gene redundancy can be due to…
gene duplication
Duplicate genes are called
paralogs (not always the same)
Example of gene redundancy
seed shape, 15:1 ratio, dominant allele will give triangle
Refers to a pattern in which modification occurs to a nuclear gene or chromosome that alters gene expression
epigentic inheritance
What does not change over many generations
DNA sequence
Two ways to obtain epigenetic inheriteance
- chromosomal dna is not naked in cell but covered in proteins that stick to it. gene copies are expressed different because proteins are binding the copies of the gene different.
- chromosomal dna can be chemically modified by added methyl group
Adding a methyl group onto chromosomal dna has what effect?
cause genes to be less expressed or turned off
Phenomenon in which expression of a gene depends on whether it is inherited from the mom OR dad
Genomic imprinting
Genomic imprinting is another example of…
monoallelic expression
The slient allele in genomic imprinting is known as
imprinted allele
Random X inactivation is an example of
monoallelic expression
Epigenetic inheritance allele is expressed in euchromatin
monoallelic expression
In random x inactivation, the chromosomes become….
more condensed and a barr body is formed
Imprinting results in the expression of the ___ but not the ___ allele
paternal, maternal
The imprinted allele is the silent one so that Igf2 gene is…
maternally imprinted
Dosage compensation occurs when ___ is not expressed
X in males
Dosage compensation is only epigenetic inheritance in…
marsupials
X inactivation brings about….
Dosage compensation
The purpose of Dosage compensation is to….
offset the differences in the number of genes on the sex chromosomes
X-linked gene dosage compensation in human females occurs by:
condensation throughout one of the two X chromosomes in females to form a ‘Barr Body’
Klinefelters syndrome
male XXY
Turner syndrome
X0, female
Triple X syndrome
XXX, female
The ____ it the thing that binds the sister chromatids of a chromosome originally inherited from mom to the sister chromatids of a homologous chromosome inherited from dad
synaptonemal complex
Cell not in cell cycle is in
G0
Incomplete dominance occurs because
A. a gene is found on the X chromosome
B. the dominant allele is not expressed due to environmental effects
C. 50% of the normal protein is not enough to produce the same phenotype as 100% of the protein.
D. the recessive allele inhibits the expression of the dominant allele
C
Chloroplasts originated as
cyanobacteria
mitochondria originated as
nonsulfer purple bacteria
The endosymbiotic origin of organelles is supported by what observations?
organelles have circular chromosomes (like bacteria)
Organelle genes are more similar to bacterial genes than to those in the nucleus.
Chloroplasts are only inherited from the ___. What kind of leaves?
mother, white or variegated
Mitochondria are inherited from
mom
Mitochondrial mutations may occur in ____cells. Why?
somatic; they are susceptible to DNA damage
protein recruits proteins to create a new bacterial cell wall
FtsZ protein
