BIOL1003 Study Guide - Final Guide: Achondroplasia, Gregor Mendel, Abo Blood Group System

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16 May 2018

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Mendelian Genetics

Blending Inheritance

• The belief that offspring carry a blend of characteristics from both parents.

Particulate Inheritance

• Particulate inheritance – phenotypic traits can be passed from generation to generation

through disrete partiles kow as gees, whih a keep their ailit to e epressed

while not always appearing in a descending generation.

• Discovered by Mendelian genetics theorists, eg: Gregor Mendel (1822-1884).

• Garden peas artificially crossed by transferring pollen with a brush from one flower to

another.

• Self-pollination easily prevented by emasculating flower.

Mendel's Observations

• The phenotype is determined by heritable factors (genes).

• Alternate forms of genes are responsible for variation in inherited characters ("alleles").

• For each character an organism inherits 2 genes, one from each parents (for diploid

organisms).

• If two alternative forms of a gene are present, one is dominant and one is recessive.

• The two genes for each character segregate during gamete production.

• Law of Segregation – the two alleles for each gene separate during gamete formation.

• Law of Independent Assortment – alleles of genes on non-homologous chromosomes assort

independently during gamete formation.

• Mendel's 3:1 Ratio - if two F1 heterozygotes are crossed, 3 will show the dominant trait and 1

will show the recessive.

• Recessive disorder in humans - albinism, phenylketonuira (PKU).

• Dominant disorders in humans - achondroplastic dwarfism, Huntington disease.

• In incomplete dominance, three distinct phenotypes are evident, i.e. the third phenotype in

which the expressed physical trait is a combination of the phenotypes of both alleles.

• 2 homozygous parents → F1 offspring heterozygous for flower colour → F2 offspring - 3

phenotypes in 1:2:1 ratio, eg: snapdragons.

• Eg: Human blood groups - the ABO group shows dominant, recessive and codominant alleles -

A and B are codominant, and dominant to O.

• Eg: Sickle cell anaemia - this new allele affects the structure of the rbcs giving them a "sickle"

shape.

o Heterozygotes who have one copy of the normal haemoglobin allele and one copy of the

sickled allele have some sickled cells and some normal cells.

o They are mildly anaemic but 1/4 of the children of two heterozygotes have severe anaemia.

Sex Chromosomes

• The Y-chromosome - very few genes on the Y chromosome and most have some function in

sex-determination or male sexual development.

• The X chromosome - contains 2000 of our 2500 genes. Most have important functions in both

sexes and have nothing to do with sex-determination.

Sex-Linked Inheritance

• If a male has a damaged gene on his X chromosome, there is no second copy to provide

back-up (like females) and so he will be affected.

• So X-linked recessive conditions will be much more common in males than females.

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Related Questions

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.