DAT Bootcamp: Chapter 7: Heredity

gene

a distinct unit, or sequence, of genetic material that codes for a trait

locus

refers to where the gene is located within the genome; For humans, this would indicate on which of the 23 chromosomes a gene is located, and its physical location on that gene.

allele

An alternative version of a gene. An example is eye color: blue, green, and brown eyes are different versions of the eye color gene.

wild type

a _____ allele is the 'normal' copy of an allele

mutant

A _____ allele has an altered DNA sequence that can affect a gene's phenotype

genotype

refers to the actual DNA sequence of a gene

phenotype

refers the observable characteristics of that gene's expression

homologous

_____ chromosomes: a pair of chromosomes (one maternal and one paternal) that contain all the same genes in the same location (but not necessarily the same alleles, as each parent may contribute different alleles for a given gene).

22

Humans have _____ pairs of autosomal chromosomes and one pair of sex chromosomes.

autosomal

Humans have 22 pairs of _____ chromosomes and one pair of sex chromosomes.

homologous

In females (XX), the sex chromosomes are _____ but in males (XY) they are not.

homozygous

An organism is considered to be _____ for a given gene if an identical allele is

present on each homologous chromosome.

dominant

Homozygous-_____ individuals carry two

copies of the dominant allele (e.g. BB)

recessive

homozygous-_____ individuals carry two

copies of the recessive allele (bb)

heterozygous

An organism that is _____ for a given gene carries a copy of the recessive allele on

one of their homologous chromosomes and a copy of the dominant allele on their other

homologous chromosome (e.g. Bb).

hemizygous

_____ refers to the condition of having a single copy of a gene instead of two.

❖ E.g. men have two different sex chromosomes (XY), and are therefore "this" for the genes present on each chromosome.

law of segregation

Mendel's law that states that, since homologous chromosomes separate during anaphase I of meiosis, each parent only passes one of their alleles for a trait to their offspring

law of independent assortment

Mendel's law that states that one chromosome does not affect another as they separate during meiosis

law of dominance

Mendel's law that states that the dominant allele will mask the effect of a recessive allele

monohybrid

a _____ test cross is used to test a single gene

dihybrid

a _____ test cross is used to test two genes simultaneously

P

label for parental generation in a test cross

F1

label for first generation of offspring in a test cross; offspring of parental generation

F2

label for second generation of offspring in a test cross; result of breeding offspring of parental generation

multiply

To determine probabilities in a dihybrid cross, it is often easier to calculate the probability of each gene separately, then _____ the results together.

chromosomes

in a dihybrid cross, gene loci must be on separate _____ for this experiment to be successful.

incomplete dominance

pattern of inheritance in which the expression of alleles is blended, producing a unique heterozygous phenotype; example: Rr = pink (not red or white)

codominance

pattern of inheritance in which both alleles are completely expressed; examples: blood type AB; Rr = flower petals with red and white patches

multiple alleles

pattern of inheritance in which more than two alleles exist for a given gene; example; ABO blood types

epistasis

pattern of inheritance in which one gene affects the phenotypic expression of a second, separate gene; example: Fur pigmentation: 1st gene controls (turns on/off) the production of pigment and the 2nd gene controls pigment color. If 1st gene codes for no pigment then 2nd gene has no effect, regardless of

pigment color gene.

pleiotropy

pattern of inheritance in which a single gene has more than one phenotypic expression; examples:

- Gene in pea plants that expresses seed texture also influences phenotype of

starch metabolism and water uptake.

- Gene causing sickle cell anemia leads to multiple health conditions.

polygenic inheritance

pattern of inheritance in which the interaction of many genes shape a single phenotype with

continuous variation; examples: height, skin color

sex-linked

_____ genes are genes that reside on a sex chromosome; example: the gene that causes color blindness is located on the X-chromosome

sex-influenced

_____ genes can be affected by sex of individual carrying trait (e.g. a Bb female not bald, Bb male is).

genomic imprinting

a specific allele is expressed (or not) depending on whether or not it is maternal or paternal. This is distinct from sex-influenced genes because the effect also occurs on autosomal chromosomes.

penetrance

the probability that an organism with a specific genotype will express the corresponding phenotype

expressivity

the term that describes the variation of a phenotype for a specific genotype; example: two people are Bb for body hair, but one person is very hairy and the second person less so

x-inactivation

During embryonic development in female mammals, one of two X chromosomes does not uncoil. Instead, it forms a dark and coiled compact body chromosome (Barr body) that is not expressed. The genes on the other X chromosome will be expressed.

barr body

During embryonic development in female mammals, one of two X chromosomes does not uncoil. Instead, it forms a dark and coiled compact body chromosome (_____) that is not expressed. The genes on the other X chromosome will be expressed.

linked

_____ genes are two or more genes that reside close together on a chromosome, and are

therefore less likely to be separated by recombination during meiosis, and are more likely to be inherited together

nondisjunction

the failure of chromosome pairs or chromatids to separate during mitosis (failure of two chromatids of a single chromosome during anaphase) or meiosis (homologous chromosomes can fail to separate during meiosis I, or sister chromatids can fail to separate during meiosis II).

meiotic

_____ nondisjunction can result in gametes with missing or extra chromosomes,

creating conditions such as trisomy (three copies of a chromosome) or monosomy

(only one copy of a chromosome).

trisomy

Meiotic nondisjunction can result in gametes with missing or extra chromosomes,

creating conditions such as _____ (three copies of a chromosome) or monosomy

(only one copy of a chromosome).

monosomy

Meiotic nondisjunction can result in gametes with missing or extra chromosomes,

creating conditions such as trisomy (three copies of a chromosome) or _____

(only one copy of a chromosome).

mosaicism

_____ occurs in cells that undergo mitotic nondisjunction during embryonic

development; as a result a fraction of body cells have extra or missing chromosomes

n+1, n+1, n-1, n-1

gametes of meiosis 1 nondisjunction:

n, n, n+1, n-1

gametes of meiosis II nondisjunction:

point mutation

a _____ is a single nucleotide change causing substitution (the change of one nucleotide to a different nucleotide), insertion (the addition of a nucleotide), or deletion (the removal of a nucleotide)

substitution

a point mutation is a single nucleotide change causing _____ (the change of one nucleotide to a different nucleotide), insertion (the addition of a nucleotide), or deletion (the removal of a nucleotide)

insertion

a point mutation is a single nucleotide change causing substitution (the change of one nucleotide to a different nucleotide), _____ (the addition of a nucleotide), or deletion (the removal of a nucleotide)

deletion

a point mutation is a single nucleotide change causing substitution (the change of one nucleotide to a different nucleotide), insertion (the addition of a nucleotide), or _____ (the removal of a nucleotide)

frameshift mutation

Both insertion and deletion of nucleotides can cause a _____. This results in the 'reading frame' of an RNA transcript being shifted, causing different amino acids to be translated and resulting in impaired protein structure.

transition mutation

A _____ is when a purine nucleotide is converted to another purine, or a pyrimidine is converted to another pyrimidine.

transversion mutation

A _____ is when a purine nucleotide is converted to a pyrimidine nucleotide or vice versa.

forward mutation

A _____ changes a wild type allele to a mutant allele

backwards mutation

A _____ reverts a mutant allele to a wild type allele

aneuploidy

the condition of a genome having extra or missing chromosomes, often caused by nondisjunction

Down Syndrome

Trisomy 21; characterized by intellectual disability

Turner Syndrome

XO, missing sex chromosome; results in sterility and physical abnormalities. This is a monosomy.

Klinefelter Syndrome

XXY; results in sterility

Edwards Syndrome

Trisomy 18; characterized by heart defects

chromosomal abberations

involve changes to segments of DNA

duplications

_____ occur when a chromosome segment is repeated on the same chromosome, and can occur from unequal crossing over

inversions

_____ occur when a chromosome segment is rearranged in the reverse of its original orientation

translocations

_____ occur when a chromosome segment is moved to another chromosome. This can be reciprocal (meaning two non-homologous chromosomes swap segments) or nonreciprocal (one chromosome segment is transferred to a different chromosome - this can also be referred to as an insertion).

reciprocal

Translocations occur when a chromosome segment is moved to another chromosome. This can be _____ (meaning two non-homologous chromosomes swap segments) or nonreciprocal (one chromosome segment is transferred to a different chromosome - this can also be referred to as an insertion).

nonreciprocal

Translocations occur when a chromosome segment is moved to another chromosome. This can be reciprocal (meaning two non-homologous chromosomes swap segments) or _____ (one chromosome segment is transferred to a different chromosome - this can also be referred to as an insertion).

Robertsonian

A _____ translocation involves two different chromosomes breaking and rejoining near their centromeres.

chromosomal breakage

a _____ can occur spontaneously or be induced as a result of mutagenic agents. The fragments can rejoin or may remain unrepaired.

mutagenic agents

A physical or chemical agent that changes the genetic material of an organism; include cosmic rays, X-rays, UV rays, radioactivity, and chemical

compounds

colchicine

a mutagenic agent that inhibits spindle formation and can induce polyploidy

proto-oncogenes

_____ (e.g. ras gene) stimulate normal growth, but if mutated they can become oncogenes (genes that can cause cancer).

oncogenes

mutated forms of genes that cause normal cells to grow out of control and become cancer cells

tumor suppressor genes

_____ (e.g. p53) help prevent uncontrolled cell growth, and if mutated in a way that decreases their activity, can contribute to the onset of cancer.

autosomal dominant

inheritance pattern of a dominant allele on an autosome; if the allele is inherited

from either parent, the offspring will be affected

autosomal recessive

inheritance pattern of a recessive allele on an autosome; the offspring will only be

affected if the recessive allele is inherited from both parents

sex-linked

_____ genetic disorders are carried on either the X or Y chromosome

x-linked dominant

sex-linked genetic disorder; a dominant allele on the X chromosome. If the allele is inherited from either parent, the offspring will be affected. Cannot be passed from father to son

x-linked recessive

sex-linked genetic disorder; a recessive allele on the X chromosome. If the allele is inherited from both parents, daughters would be affected. Inheriting a single copy of the allele will result in sons being affected (as men only have one copy of the X chromosome). Cannot be passed from father to son

y-linked

sex-linked genetic disorder; an affected allele on the Y chromosome. Men only carry one copy of the Y chromosome, so if the allele is inherited from the father, any sons will be affected. Can only be passed from father to son

extranuclear inheritance

inheritance patterns involving genetic material outside the nucleus; In eukaryotes, genes also exist outside the nucleus, and can be found in mitochondria and chloroplasts. Defects in mitochondrial DNA can reduce cell's ATP production. Mitochondria passed to the zygote all come from the mother, so all mitochondrial related diseases are maternally inherited.

mother

From which parent are mitochondria inherited?

lethal

A _____ gene prevents survival of an organism.

maternal effect gene

a gene that when mutated in the mother results in a

mutant phenotype in the offspring regardless of the offspring's own genotype.

PKU

autosomal recessive disorder; Inability to produce proper enzymes for phenylalanine breakdown; degradation product phenylpyruvic acid accumulates; mental retardation

cystic fibrosis

autosomal recessive disorder that results in thick mucus build-up in respiratory tract

Tay-Sachs

autosomal recessive disorder; Lysosome defect: cannot breakdown lipids for normal brain function (fatal within the first 5 years of life)

sickle-cell anemia

autosomal recessive disorder; Defective hemoglobin due to substitution; decreases blood's ability to carry oxygen

galactosemia

autosomal recessive disorder; caused by lack of enzyme needed to convert milk sugar galactose into glucose

Huntington's Disease

autosomal dominant disorder; the nervous system degenerates; usually does not start until middle age

achondroplasia

autosomal dominant disorder; dwarfism

hypercholesterolemia

autosomal dominant disorder; excessive cholesterol in the blood; heart disease

hemophilia

x-linked recessive disorder; blood does not coagulate to stop bleeding

color blindness

x-linked recessive disorder; inability to see some or all colors

duchenne

x-linked recessive disorder; muscular dystrophy

fragile x syndrome

x-linked dominant disorder; most common form of mental retardation, a mutation of the FMR-1 gene

Down Syndrome

chromosomal disorder; Trisomy 21; developmental and intellectual delays

Turner Syndrome

chromosomal disorder; XO; sterility; typically doesn't cause mental retardation

Klinefelter Syndrome

chromosomal disorder; XXY; sterility; causes mental retardation

cri du chat

chromosomal disorder; Deletion on chromosome 5; causes mental retardation; round face, cat-like cry, microcephaly