MED BIO COMPLEX INHERITANCE

Red-green colorblindness is a sex-linked trait on the X chromosome. A man with color-blindness and a woman with no history of color-blindness in either the males or females of her family plan to have children. What is the probability that a daughter born to this couple would be a carrier? 0% 25% 50% 75% 100% WRONG

0% WRONG

How many Barr bodies would you expect to be present in a cell with the chromosomes XXXY? 1 2 3 4

2

In a female mammal heterozygous for an X-linked recessive allele, what proportion of somatic cells will express the recessive allele? 100% 25% 0% 50%

50%

The DNA of fraternal twins is _____ identical. 0% 25% 50% 75% 100%

50%

Red-green colorblindness is a sex-linked trait on the X chromosome. A man with color-blindness and a woman with no history of color-blindness in either the males or females of her family plan to have children. What is the probability that a son born to this couple would be color-blind? 0% 25% 50% 75% 100% WRONG

50% WRONG

Which of the following are common types of molecular changes that result in epigenetic effects on gene expression? DNA translocation DNA mutation Covalent histone modification Localization of histone variants DNA methylation Chromatin remodeling

Covalent histone modification Localization of histone variants DNA methylation Chromatin remodeling

The endosymbiotic hypothesis is supported by

DNA is single-stranded, which is only found in prokaryotes mitochondria have own cell membranes, like prokaryotes self reproduce like bacteria

Which of the following terms would NOT be used to describe a trait that shows variation over a range of phenotypes? Polygenic Discrete Quantitative Continuous All of the terms could be used to describe

Discrete

Discrete vs quantitative traits + examples

Discrete: clearly defined phenotypes - ex: purple flower/white flower (Pw), red eyes/white eyes; smooth corn/wrinkled corn - if you have the gene, you have the trait Quantitative: continuous variation over a range - ex: height, weight, # of apples produced - polygenic: multiple genes involved - reflect environmental influence

Define maternal inheritance (in relation to mitochondria & chloroplasts)

Egg has the mitochondria / plastids Sperm does not - mitochondria only helps to sperm swim

Which of the following statements are true regarding epigenetics? Variations of gene expression that result from DNA mutations Epigenetic changes are transmissible from cell to cell. Variations are reversible from one generation to the next. Epigenetic changes may be transmitted to offspring. Variations of gene expression that are unrelated to DNA sequence variants

Epigenetic changes are transmissible from cell to cell. Variations are reversible from one generation to the next. Epigenetic changes may be transmitted to offspring. Variations of gene expression that are unrelated to DNA sequence variants

Paternal inheritance occurs in plants but not animals because plants have chloroplasts instead of mitochondria. T/F

False

Which of the following statements most accurately defines epistasis? WRONG!!! The genotype of the mother determining the phenotype of the offspring. The inheritance of two or more genes close together on the same chromosome The alleles of one gene masking the dominant alleles of another gene. A single gene affecting a single trait. Inactivation of the allele from one parent and expression of the the allele from the other parent.

Inactivation of the allele from one parent and expression of the the allele from the other parent. WRONG

How does DNA methylation inhibit gene expression? It causes mutations in the gene. It attracts activator proteins to the promoter. It causes chromatin to become more compact. It prevents the initiation of transcription. It prevents binding of repressor proteins.

It causes chromatin to become more compact. It prevents the initiation of transcription.

Describe how linked genes violate the law of independent assortment. Linked genes are typically inherited together. Explain why.

Linked genes: genes are on the same chromosome - ex: AB on chromosome 1 get inherited together independent assortment: traits (genes) that are inherited independently are on different chromosomes ex: - assumed flower color & pollen shape would be inherited independently (equal possibility for combos) - saw: purple flowers mostly have long pollen; red flowers mostly round pollen

What is the phenomenon called in which a trait of the offspring is solely determined by the value of the trait in the female parent because it is passed on via the organelles in the egg cell? Maternal inheritance Gene linkage Epistasis Genomic imprinting Maternal effect

Maternal inheritance

Leaf pigmentation in four-o'clock plants is inherited via the chloroplast genome. A female plant with variegated leaves is crossed with a male plant with white leaves. What is the result of this cross? Half of the offspring will have variegated leaves, and the other half will have white leaves. All offspring will have white leaves. All offspring will have variegated leaves. Some offspring will have green leaves, some will have white leaves, and some will have variegated leaves. All offspring will have green leaves.

Some offspring will have green leaves, some will have white leaves, and some will have variegated leaves.

Chloroplast and mitochondrial genes in mammals and plants are generally inherited from the mother. T/F

True

Epistasis often involves genes of an enzymatic pathway. T/F

True

In our case study, we learned that the correct functioning of the reelin signalling pathway is important for coordinating brain development, learning, and memory T/F

True

What is an example of epigenetic inheritance?

X chromosome inactivation

Do mitochondria and chloroplasts have their own genome?

Yes, they have DNA but no nucleus! how? - endosymbiosis

The genomes of mammalian mitochondria contain genes whose products are used in translation of mRNA. ribosomal genes. genes for proteins used in oxidative phosphorylation. a total of 37 genes. All of the items listed are correct.

all of the items listed are correct

Which of the following organelle(s) has/have a genome separate from the genome in the cell nucleus?

both the mitochondria and chloroplasts

Linked genes generally do not follow the laws of independent assortment. are polygenic. reflect a pattern of codominance. show pleiotropy.

do not follow the laws of independent assortment.

Epistatic genes are typically part of a metabolic pathway. Explain why

each step of metabolic pathway is controlled by different enzymes, which are coded for by various genes - variations in alleles may result in an inactive enzyme - inactive enzyme will halt metabolic pathway & product wont be formed - one gene has control over the whole pathway Sweet pea example: - 2 true breeding white varieties of sweet peas - expected all white offspring - F1 was all purple - F1 crossed -> F2: 9:7 ratio - why? - theres not a gene for purple two genes for color: - P: purple; p: white - C: purple; c: wite For a flower to be purple, must have at least 1 dominant allele at each locus - PPcc = white pathway to produce a purple flower: - colorless precursor -> colorless intermediate -> purple pigment for a flower to be purple, each step has to work - we need to have a working enzyme/dominant allele at each step (C & P)

Define X chromosome inactivation

everyone needs one X females get 2 - one X gets randomly inactivated (condensed early in embryonic development how? - X chromosome is compacted/condensed into a barr body barr body: structure in cell nuclei of females, consists of a condensed inactive X chromosome

The inheritance pattern observed for genes that are located outside the cell nucleus, in mitochondria or chloroplasts, is called ______ inheritance.

extranuclear

Fur color of cats & X chromosome inactivation example

fur color is sex linked early embryo - all X are active - 2 XX chromosomes in each cell: one w/ gene for orange & one for black - random inactivation/compaction of one of X chromosomes occurs - each cell gives dif patch of fur (depends on which color gene was on the compacted chromosome) patterns of X chromosome inactivation maintained during division & passed to descendants of cell

Individuals may have the same genotype but very different phenotypes as a result of ______. epistasis genetic linkage polygenic inheritance genomic imprinting

genomic imprinting

A horticulturist is breeding a new variety of houseplant in which two genes control leaf color. G (allele for green) is dominant to g (yellow) and B (second allele for green) is dominant to b (yellow). The recessive homozygous condition of either gene will mask a dominant allele. What color is a plant with the genotype GgBb? green variegated (yellow and green spots or stripes) yellow an intermediate yellow-green the color cannot be determined with the information given.

green

Maternal Inheritance in Humans

human mitochondrial diseases show maternal inheritance pattern if dad has disease, you won't inherit

How does genomic imprinting work?

imprinted genes - we inherit one working (expressing) copy silencing usually happens via methylation during gamete formation - methylation -> turn off gene so, an allele inherited from mother may be silencing, the same allele from father may be expressing pattern is passed to zygote, when zygote begins producing gametes the methylation pattern is erased - both alleles have potential to be expressed example - male & female inherit alleles w/ the pattern: - mother: silencing (methylated) - father: expressing zygotes grows into female/male w 2 copies of an allele on a chromosome, but one from mother is silenced zygotes grow & start forming gametes (pattern erased) - during egg formation, female always has methylation of both alleles - male has no methylation so, - if female has offspring: both are silenced, doesn't matter what alleles she donated - if male has offspring: both alleles would be expressed the male inherited a silenced gene from his mother that is transcriptionally silenced in his somatic cells - he does not express this gene during his lifetime, but he can pass on an active copy of the exact gene to his offspring

define epigenetic inheritance

inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence

epigenetic gene regulation - key points - inheritance

key points: - genetic code not changed - only changes regulation of gene expression (methylation, histones, nucleosomes) inheritance: patterns of gene regulation are inherited - to all the descendants of a particular cell - to offspring of an organism - over 1 or 2 generations

In humans, mitochondria are inherited through a type of uniparental inheritance called ________ inheritance.

maternal

Methylation & genomic imprinting

methylation: suppresses gene activity and expression - allele becomes silenced

Mendelian genetics vs complex inheritance

most traits aren't controlled by a single gene - characters are more complex environmental influence epigenetic gene regulation inherited patterns of linked genes don't follow law of independent assortment

Do humans inherit their mitochondria from their mother or their father or both?

mother only

Define genomic imprinting

produces different patterns of gene regulation (expression) depending on whether the gene was inherited from mother or father example of chromosome inactivation this is how you can pass genes that you don't express to offspring

linked genes, crossover frequency, & location of genes on a chromosome

prophase 1: crossover genes that are farther away from each other on the same chromosome will have a higher rate of crossover (genetic exchange w other chromosome) - closer together = less likely - change in linked inheritance pattern called recombination frequency - high = farther - low = closer

Polygenic traits & skin color example

skin color - controlled by multiple genes for pigment production genes = potential actual amount of pigment produced will depend on genes + environment

endosymbiosis

some early eukaryotic cells were formed from simpler prokaryotes (cells joined together) mitochondria & chloroplasts are descendants of ancient symbiotic relationships between archaean cells & bacteria - they divide to make more mitochondria & plastids - each has its own genome mitochondria makes mitochondria, plastids make plastids

Imprinted genes do not follow a Mendelian inheritance pattern because ______. the alleles from the parents are expressed differently individuals with imprinted genes are mosaics with different expression patterns in different somatic cells the DNA sequence is altered in each generation

the alleles from the parents are expressed differently

Define epistasis

the expression of one gene is modified (e.g., masked, inhibited or suppressed) by the expression of one or more other genes

In cats, a fur color gene is on the X chromosome. At this locus, cats can have a black allele or an orange allele. Cats who are homozygous for the black allele have black fur, cats who are homozygous for the orange allele have orange fur, and cats who are heterozygous at this locus are tortoiseshell. What offspring would you expect from a cross between an orange female and a black male? tortoiseshell females and tortoiseshell males tortoiseshell females and black males tortoiseshell females and orange males orange females and black males black females and orange males

tortoiseshell females and black males