BICD 100 Lecture Notes - Penetrance, Mendelian Inheritance, Epistasis

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marooneagle231

4 Jun 2018

School

UCSD

Department

Biol/Genetics,Cellular & Develop

Course

BICD 100

Professor

All

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Pedigree Inheritance Pattern Guidelines by Kirstin Barr

**These are just some of the things to look for (general trends) in pedigrees for different

inheritance patterns. These only apply when we are following Mendelian Genetics Rules (i.e. no

epistasis, incomplete penetrance, variable expressivity, etc.)**

Autosomal

• Dominant:

o if child affected, then at least one parent must also be affected

o in family branches with the disease, it should appear in every generation

• Recessive:

o You can have affected children with unaffected parents

o May skip generations

o Affected mother and father: all children will be affected

Sex-Linked

• Y-linked:

o only males will be affected

o An affected father will pass to all of his sons

• X-Linked Dominant:

o An affected male will pass to all his daughters

o Affected mother and healthy father: at least 50% of the offspring will be affected

• X-Linked Recessive

o Affected mother will pass to all her sons

o Affected mother and father: all children will be affected

o Affected father and carrier mother: 50% of daughters and 50% of sons will be

affected

o Carrier mother and unaffected father: no daughters and 50% of sons will be

affected

Things to keep in mind

• When looking at phenotypic ratios in the offspring, what is in the pedigree may not

exactly fit the expected ratio, but it can still be that model

• If the trait is RARE and RECESSIVE, you can assume all outsiders are homozygous

dominant (i.e. not carriers) unless proven otherwise by the offspring

• Once you decide on a certain inheritance pattern for a given pedigree, look to see if

there are any individuals who dispute your hypothesis.

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Related Questions

18. Which of the following statements about a pedigree would be most definitive in differentiating an AD from an XLD pattern of inheritance?

	A.	Affected males and females are seen in all generations.
	B.	An affected male has only one daughter, and that daughter is affected.
	C.	There are two instances where an uaffected parent has an affected parent and an affected child.
	D.	An unaffected male with an affected father has three affected daugthers.
	E.	An unaffected mother with an affected mother has one affected daughter and one affected son.

20. If a man and his maternal uncle express an X-linked recessive disease, we can draw the following conclusion(s):

	A.	His maternal grandma was a carrier
	B.	All of his maternal uncles must be affected
	C.	All of his daughters will be carriers
	D.	All of his sisters are carriers
	E.	All of his maternal aunts are carriers
	F.	A and C
	G.	A and D

When someone is said to have inherited a predisposition to cancer, what is meant by that?

There is a germ-line mutation

The gene involved shows incomplete penetrance

The disorder has variable expressivity

There is a somatic mutation

Imagine you observe the following in a data set: more males affected than females; approximately half the grandsons of affected males are affected; some females are affected but usually only if their maternal grandfather was affected and their mother married an affected male. What type of inheritance might you suspect?

sex-linked recessive

autosomal dominant,sex-limited

sex-linked dominant

recessive epistasis

A cross of fruit flies was conducted. White-eyed males were cross with pink-eyed females. All F1 flies had normal eye color. F1âs were intercrossed yielding F2 flies as follows: 890 wildtype females, 455 wildtype males, 605 white-eyed males, 140 pink-eyed males, and 310 pink-eyed females. Give a genetic explanation consistent with these data.

white is autosomal recessive and epistatic to pink

pink is autosomal recessive and dominant over white

pink and white are x-linked recessive with white dominant to pink

white is x-lined recessive, pink is autosomal recessive; white is recessive epistatic to pink

An avid gardener decides to plant seeds from disk-shaped squashes she raised during the previous summer. To her surprise, 89 of her plants bear disk-shaped squashes while 61 plants produce spherical squashes and 10 produced elongate shaped squash. What is the mode of inheritance of fruit shape in these squash?

Codominance

Recessive epistasis

Duplicate interaction

Epistasis

Based on what you know about translation, what does âreverse translationâ mean?

Determining a DNA sequence from an amino acid sequence

Determining a RNA sequence from a DNA sequence

Translating in the 3â to 5â direction

Transcribing first, then translating

If an organismâs diploid chromosome number is 18, how many different possible combinations of homologous chromosomes lining up during meiosis exist for the eggs or sperm produced by that organism?

	A.	512
	B.	9
	C.	18
	D.	128
	E.	36

At the end of metaphase I, _______________ separate.

	A.	sister chromatids
	B.	germ cells
	C.	homologous chromosomes
	D.	haploid chromatids
	E.	centrioles

Mendel observed that dominant traits

	A.	are seen in all of the F1 hybrid pea plants in his experiments.
	B.	are expressed in all plants.
	C.	were absent in the F1 generation of pea plants that he used in his experiments.
	D.	were the only traits seen in the F2 generation of pea plants in his experiments.
	E.	are only expressed in hybrids.

Cytokinesis in plant cells differs from cytokinesis in animal cells because

	A.	there is no difference.
	B.	in plant cells, the cell plate must also divide into two parts.
	C.	the contractile protein, actin, is important only in plant cells.
	D.	plant cells have a rigid cell wall.
	E.	a contractile ring forms only in plant cells.

Sickle cell anemia is an example of what type of inheritance?

	A.	complete dominance
	B.	incomplete dominance
	C.	codominance
	D.	multiple alleles
	E.	recessive dominance

Which of the following statements is true:

	A.	The dominant allele is masked in homozygous dominant individuals.
	B.	With recessive genetic disorders, if both parents are carriers, the offspring will all be affected.
	C.	In carriers, the recessive allele causes an intermediate phenotype.
	D.	In recessive genetic disorders, the mother and/or father of an affected individual must also be affected.
	E.	With dominant genetic disorders, the mother and/or father of an affected individual must also be affected.

Skin cancers typically develop in the

	A.	upper layers of the epidermis.
	B.	lower layers of the dermis.
	C.	subcutaneous layer.
	D.	lower layers of the epidermis.
	E.	upper layers of the dermis.

Duchenne muscular dystrophy (MD) is inherited from an X-linked recessive allele. What is the probability that a son with Duchenne MD inherited this disease from his biological father?

	A.	1/2
	B.	0
	C.	1/16
	D.	1/4
	E.	1/8

The genetic makeup of a particular trait in an individual is its

	A.	genotype.
	B.	heterozygosity.
	C.	phenotype.
	D.	filial.
	E.	dominance.

What structure holds the sister chromatids to the spindle fibers?

	A.	chromatin
	B.	kinetochore
	C.	MPF
	D.	centromere
	E.	cyclin

If you view a cell in which the genetic material is beginning to be visible as separate bodies, and the nucleus has disappeared from view, you may surmise that the cells is in

	A.	telophase.
	B.	anaphase.
	C.	interphase.
	D.	metaphase.
	E.	prophase.

Gregor Mendel was successful in his analysis of the genetics of pea plants because

	A.	he examined and analyzed both the F1 and F2 generations.
	B.	he studied the parental plants to determine their differences.
	C.	he decided to only look at his results in an objective manner.
	D.	he studied a trait that had a strange inheritance pattern.
	E.	pea plants have genetics different from other organisms.

Tall corn plants (T) are dominant to dwarf plants (tt). Solid green leaves (G) are dominant to leaves with a white tip (gg). A cross between two corn plants yielded the following phenotypes: 51 tall plants with a white tip on their leaves; 43 dwarf plants with solid leaves; 48 dwarf plants with white tips on their leaves; 45 tall plants with solid leaves. What are the genotypes of the parents that produced these plants?

	A.	None of the above
	B.	TtGg x Ttgg
	C.	ttGG x TTgg
	D.	TtGg x TtGg
	E.	TtGg x ttgg

In humans, a gene that has been identified as causing a type of skin cancer is the

	A.	superwoman echidna.
	B.	mutant superman.
	C.	sonic hedgehog.
	D.	mutant mole rat.
	E.	superhero aardvark.

The segregation principle states that in sexually reproducing diploid organisms the two copies of each gene

	A.	segregate from each other during meiosis.
	B.	must always be the same allele.
	C.	separate from each other during mitosis.
	D.	will both wind up in either the sperm or egg.
	E.	move together as a unit during meiosis.

In what phases is the genetic material in the cell correctly referred to as chromatids?

	A.	metaphase and telophase
	B.	anaphase and metaphase
	C.	interphase and telophase
	D.	interphase and prophase
	E.	metaphase and prophase

Consider two traits for an organism, determined by two genes, each of which is governed by at least two alleles. In the case of a dihybrid individual, the gametes formed will be of either the parental type or the recombinant type. Recombinant type gametes are formed because of

	A.	the principle of dihybrids.
	B.	multiple alleles.
	C.	heterozygosity.
	D.	incomplete dominance.
	E.	independent assortment.

An allele is

	A.	an alternate form of a gene.
	B.	always recessive.
	C.	the main factor determining a trait.
	D.	always one of a pair.
	E.	the dominant form of a gene.

After the DNA is replicated, and it condenses in prophase, two identical rods of DNA are seen. These are

	A.	spindle fibers.
	B.	kinetochores.
	C.	chromatids.
	D.	chromatin.
	E.	centromeres.

Special cells found in the gonads that give rise to gametes upon division are called

	A.	egg cells.
	B.	somatic cells.
	C.	germ cells.
	D.	stem cells.
	E.	basal cells.

BICD 100 Lecture Notes - Penetrance, Mendelian Inheritance, Epistasis

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