Section 6: Heredity Flashcards
To determine the probability of two or more independent events occurring, what should be done with their individual probabilities?
Multiply them by each other
This is the genetic material on a chromosome for a trait
Gene
This is the location on a chromosome where the gene is located
Locus
This is the variance of genes that can lead to different things like colors
Allele
These are a pair of chromosomes that contain the same genetic material, gene for gene.
Each parent contributed 1 of the chromosome in the pair and thus different alleles may exist for a gene
Homologous chromosomes
One member of each chromosome pair migrates to an opposite pole so that each gamete is _______ (aka each gamete has only one copy of each chromosome), occurs in anaphase I.
haploid
This is known as the law of segregation
migration of homologues within one pair of homologous chromosomes does not influence
the migration of homologues of other homologous pairs (independent assortment of alleles)
Law of independent assortment
This involves the breeding of a dominant trait individual with a recessive individual, in order to determine the zygosity of the former by analyzing proportions of offspring with the recessive phenotype. Determines if hetero or homo dominant.
These test one gene
These test two (on different chromosomes)
Test crosses
Monohybrid cross test
Dihybrid Cross Test
What are the generations for test crosses?
P(parental), F1, F2 etc
This is the blending of expressions of alleles, developing a unique hetero phenotype
ex:R red, R’ white, RR’ comes out pink
Incomplete dominance
This occurs when both inherited alleles are completely expressed (e.g. blood types A and B or both can show up as AB if expressed)
Codominance
Blood groups have 3 possible alleles, the codominant A and B and the O, leading to 4 possible genotypes
(phenotypes?): AO (A type), BO (B type), AB (codominant AB type), OO (O type
Multiple alleles
One gene affects phenotypic expression of 2nd gene.
What’s an example of this?
Epistasis
Pigmentation
In pigmentation, an example of epistasis, one gene is turn on/off and the 2nd gene controls the color amount. If the 1st gene codes for no pigment, does the 2nd gene have any effect?
Ex: CCBx => black fur in mice
ccxx =>no pigment
No.
single gene has more than 1 phenotypic expression
For example, the gene in pea plants that expressed seed texture also
influences phenotype of starch metabolism and water uptake; sickle cell anemia leads to different health conditions
Pleiotropy
The interaction of many genes to shape a single phenotype w/ continuous variation (height, skin color)
Polygenic inheritance
two or more genes that reside on the same chromosomes and thus cannot separate independently because
they are physically connected (inherited together). They exhibit recombination about 18% of the time.
Linked Genes
In a cross of BbVv x bbvv (says that BV and bv are linked and each is in a homologues). We only get BV or bv and no Bv or bV. However, if there is recombination, we may get 18% of Bv and bV
What does a greater recombination frequency mean?
Linked Genes
Farther distance of genes apart on the same chromosome
In linked genes, Linkage map: B-V is 18%, A-V is 12%, and B-A is 6%, so what is the approximate spacing?
B——A————V ‘-‘ = 1 unit apart
Refers to single gene resides on sex chromosome; when male (XY) receives an X from mother, whether it is
dominant or recessive will be expressed because there is no copy on the Y chromosome
Sex-linked
can be influenced by sex of individual carrying trait (e.g. Bb female not bald, Bb male is)
Sex-influenced
probability an organism with a specific genotype will express a particular phenotype`
Penetrance
term describing the variation of phenotype for a specific genotype
Expressivity
This occurs during embryonic development in female mammals, one of two X chromosomes does not uncoil into
chromatin
What is the dark and coiled compact body chromosome?
Can it be expressed?
X-inactivation
Barr body
No, so only the genes on the other X will be expressed.
As an example of X-inactivation, calico cat females can be heterozygous for fur color, which usually leads to orange fur because the orange trait is dominant. But in females it can also lead to black. Why?
The dominant orange fur gene has been inactivated and turned into a barr body
This is another example of X-inactivation, where the female cannot form a blood clot.
XHXh is a normal carrier, but if XH is inactivated, Xh is expressed
Hemophelia
This is the failure of one/more chromosomes pairs or chromatids to separate during mitosis or meiosis
Nondisjunction
Nondisjunction in meiosis or mitosis:
The failure of two chromatids of a
single chromosome during anaphase
mitosis
Nondisjunction in meiosis or mitosis:
homologous chromosomes to separate during Meiosis I or sister chromatids to separate during Meiosis II;
result in trisomy or monosomy; ex Down syndrome
note: specifically during anaphase!
Meiosis
This occurs cells that undergo nondisjunction in mitosis during embryonic development; fraction of body cells have extra or missing chromosome
Mosaicism
This occurs all chromosomes undergo meiotic nondisjunction and produce gametes with twice the number of
chromosomes. Common in plants.
Polyploidy
This is a human genetic defect where a single nucleotide changes causing substitution, insertion, deletion (latter 2 could cause frameshift).
Point Mutation
This is a point mutation from purine to purine or pyrimidine to pyrimidine
This is a point mutation from purine to pyrimidine or vice versa
Transition mutation
Transversion mutation
A genome with an extra/missing chromosome, often caused by nondisjunction (down syndrome = trisomy 21)
Aneuploidy
This disease is nondisjunction in sex-chromosome. Gametes can be XX/XY or O (no chromosome). XO is sterile, physically abnormal. It may be missing on some or all
Turner Syndrome
This genetic defect is marked by the XXY genotype
This is marked by Trisomy 21
Klinefelter
Down Syndrome
These occur when chromosome segments are changed
This is repetition of a segment on the same chromosome
This is rearrangement of the segment in the reverse orientation
This is movement of the segment to another chromosome (can cause downs as well)
Chromosomal Abberations
Duplicatoins
Inversions
Translocation
These are spontaneous or induced (mutagenic agents, Xrays). A deficiency means there was a lost fragment
Chromosomal Breakage
These include cosmic rays, Xrays, UV rays, radioactivity, chemical compounds include colchicine (inhibits
spindle formation causing polyploidy), mustard gas. They are generally also carcinogenic
Mutagenic Agents
Proto-oncogenes stimulate normal growth; if mutated become ____ which leads to cancer
Oncogenes
AR genetic disorders include
The inability to product proper enzyme for phenylalanine breakdown; degradation
product phenylpyruvic acid accumulate
PKU
AR genetic disorders include:
fluid builup in tracts
lysosome defect, can’t break down lipids for normal brain fxn
defective Hb due to substitution mutation
Cystic fibrosis
Tay-sachs
Sickle Cell Disease
This genetic disorder results from degenerate nervous system tissue
This one is abnormal blood clotting
Also color blindness
Huntington’s disease
Hemophelia
Which of these doesn’t typically cause mental retardation:
Downs, Turner, Klinefelter,
Turner’s syndrome
This term means an already mutated organism mutates again even more
This one means it mutates back to the original
Forward mutation
Backward mutation
Extranuclear genes are found in mitochondria and chloroplasts. Defects in mito DNA can reduce
cell’s ATP production. What type of inheritance is this?
Mitchondria passes to zygote all come from FATHER/MOTHER
Extranuclear inheritance
Mother
Note: mitochondria have their own ~70S ribosomes that make mitochondrial proteins within the mitochondrial matrix
If the phenotype “skips” generations be suspicious of an….
If no skip, it is most likely
If a father doesn’t have a particular phenotype, none of his daughters display it in _______
Autosomal recessive disorder
Autosomal dominant
X-linked recessive
This type of DNA is an exception an exception to the universality of the genetic code
Mitochondrial DNA
