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Flashcards in Heredity Deck (59):
1

What is Heredity?

To determine the probability of 2 or more independent events occurring together multiply the properties of each separate event.

2

Gene:

Genetic material on a chromosome for a trait.

3

Locus:

Location on chromosome where gene is located.

Every gene has a unique locus on a particular chromosome.

4

Allele:

Variance of genes such as different color.

5

Homologous Chromosomes:

refers to a pair of chromosomes( a HOMOLOGOUS PAIR) that contains the same genetic information, gene for gene. Each parent contributed one of the chromosomes in the pair. At any one particular locus, the two genes on a pair of homologous chromosomes (a GENE PAIR) might represent two different alleles for that gene because they originated from different parents.

For example, the allele for flower color on one pea plant chromosome(inherited from one parent) might code for purple flowers, whereas the allele on the homologue of that chromosome(inherited from one parent) might code for white flowers.

6

Law of segration

States that allele pairs separate or segregate during gamete formation,

In other words, one member of each chromosomes pair migrates to an opposite pole so that each gamete contains only one copy of each chromosome(and each allele)

7

Law of independent assortment:

Mendells second law states that genes for one trait are not inherited together with genes of another trait.

8

Monohybrid cross

an experiment in which only one trait is being investigated.

For example, a cross between a purple-flowered pea and a white-flowered pea is a MONOHYBRID CROSS because it is investigating a gene for only one trait, the gene for flower color

9

Incomplete Dominance:

Characterized by blending. Blending of expressions of alleles(e.g. R red, R white, RR comes out pink)

10

Codominance:

Codominance is a relationship between two versions of a gene.

Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked.

11

Multiple alleles:

Blood groups have 3 possible alleles, the codominant A and B and the O, leading to 4 possible genotypes

AO(A type), BO( B type), AB(codominant AB type), OO (O type)

12

Epistasis:

Two separate genes control one trait: but one gene masks the expression of the other gene. The gene that masks the expression of the other gene is EPISTATIC to the gene it masks.

13

Epistatis: Pigmentation

One gene controls (turn on/off) the production of pigment, and 2nd gene controls color or amount.

If 1st gene codes for no pigment ---> 2nd gene has no effect.

CCBx=> Black fur in mice ccxx => no pigment

14

Pleiotropy

The ability of one single gene to affect an organism in several or many ways.

Example: Dwarfism or Gigantism

15

Polygenenic Inheritance:

the interaction of many genes to shape a single phenotype w/ continuous variation(height, skin, color)

16

Linked genes:

When two genes are close together on the same chromosome, they do not assort independently and are said to be linked. Whereas genes located on different chromosomes assort independently and have a recombination frequency of 50%, linked genes have a recombination frequency that is less than 50%.

17

Briefly explain dominant and recessive

Dominant: the actual trait that is expressed
Recessive: represented by the gene with the lowercase letter.

18

Phenotype

is the actual expression of a gene.

Purple flowers, blue eyes, and brown hair each represent the phenotype of their respective genes.

19

Genotype:

represents the actual alleles.

For example, PP describes the genotype for the homozygous dominant condition.

Ex: The genotype Pp would express the phenotype of purple flowers.

20

Homozygous dominant

Refers to the inheritance of 2 dominant alleles (PP), the dominant trait is expressed.

21

Homozygous recessive

two recessive alleles are inherited (pp) and the recessive trait is expressed.

22

Heterozygous

refers to the condition where the two inherited alleles are different(Pp)

23

Dihybrid cross

Occurs when 2 traits are involved.

A cross investigating seed color(yellow,white) and seed texture (round,wrinkled)

24

Linkage map

A chromosome map created in a fashion that portrays the sequence of genes on a chromosome.

25

Sex-linked

Are traits that are controlled by the genes found on sex chromosomes. For example, baldness is a sex-linked trait found in men.

26

Autosomes

Of the 46 human chromosomes, 44 (22 pairs) are AUTOSOMES and 2 are SEX CHROMOSOMES, X and Y.

Traits carried on the X chromosome are called sex-linked.

27

Recessive mutation

If a sex-linked trait is due to a RECESSIVE MUTATION, a female will express the phenotype only if she carries two mutated genes (X-X-)

28

Dominant mutation

If a sex-linked trait is due to a dominant mutation, a female will express the phenotype with only one mutated gene (X-X).

29

Common examples of recessive sex-linked traits are

color blindness, hemophilia, and Duchenne muscular dystrophy.

30

Sex-influenced

Can be influenced by sex of individual carrying trait( e.g. Bb female not bald, Bb male is)

31

Expressivity:

term describing the variation of phenotype for a specific genotype.

32

Sex chromosomes

the X and Y chromosomes. All other chromosomes are called AUTOSOMES.

33

X-inactivation:

Occurs during embryonic development in female mammals, In X-inactivation, female embryos randomly inactivate one X chromosome in each cell, resulting in only one functional copy of X-linked genes in both males and females.


one of two X chromosomes does not uncoil into chromatin => dark and coiled compact body chromosome ( BARR BODY) => cannot be expressed. => genes in the female will not be expressed so similarly, so all cells in a female mammal not necessarily functionally identical.

34

Hemophilia:

Cannot form blood cot. (X^H)(X^h) is a normal carrier. But if (X^H) is inactivated => (X^h) is expressed.

35

Nondisjunction:

failure of one/more chromosomes pairs or chromatids to separate during mitosis(failure of two chromatids of a single chromosome during anaphase) or meiosis(homologous chromosomes to separate during Meiosis I or sister chromatids to separate during Meiosis II; result in trisomy or monosomy; ex Down Syndrome) ---specifically during Anaphase!

36

Mosaicism

in cells that undergo nondisjunction in mitosis during embryonic development; fraction of body cells have extra or missing chromosome

37

Polyploidy:

When a cell or organism has extra sets of chromosomes.

All chromosomes undergo meiotic nondisjunction and produce gametes with twice the number of chromosomes. Common in plants.

38

Point Mutation:

Describe.
Also describe subsitution, deletion, insertion.

Occur when a single nucleotide in the DNA of a gene is incorrect. This can occur if a different nucleotide is substituted for the correct one(SUBSTITUTION), if a nucleotide base-pair is ommitted(DELETION), or if an extra base-pair is inserted (INSERTION)

39

Point Mutation:

Transition mutation

Purine to purine or pyrimidine to pyrimidine

40

Point Mutation:

Transversion Mutation

Purine to pyrimidine or vice versa

41

Aneuploidy:

is a genome with extra or missing chromosomes. These almost always lead to genetic defects It Is often caused by nondisjunction(Down syndrome = trisomy 21)

42

Turner syndrome:

Results when there is nondisjunction of the sex chromosomes.Sperm will have either both sex chromosomes(XY) or no sex chromosomes.Individuals with Turner syndrome are physically abnormal and sterile.

43

Down Syndrome:

Occurs when and egg or sperm with an extra number 21 chromosome fuses with normal gamete. The result is a zygote with 3 copies of chromosome 21(trisomy 21).

44

Chromosomal abberations:

are caused when chromosome segments are changed.

45

Chromosomal abberations:

Duplications

occur when a chromosome segment is repeated on the same chromosome.

46

Chromosomal abberations:

Inversions:

An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself.

47

Chromosomal abberations:

Translocations

When a fragment of a chromosome becomes attached to a nonhomologous chromosome.

Segment is moved to another chromosome.

(21 on 14 can cause Down's as well, tripled 21 chunk)

48

Extranuclear Inheritance:

Extranuclear inheritance or cytoplasmic inheritance is the transmission of genes that occur outside the nucleus. It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria.

49

Phenylketonuria (PKU)

WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Autosomal recessive

Inability to break down the amino acid phenylalanine. Requires elimination of phenylalanine from diet, otherwise serious mental retardation will result.

50

Cystic fibrosis

WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Autosomal recessive

The most common lethal genetic disease in the U.S.
1 out of 25 caucasians is a carrier.
Characterized by buildup of extra-cellular fluid in the lungs, digestive tract.

51

Tay-Sachs disease
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Autosomal recessive

Onset is early in life and is caused by lack of the enzyme necessary to break down lipids needed for brain function.
It is common in Ashkenazi jews and results in seizures, blindness, and early death.

52

Huntington's disease
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Autosomal dominant

A degenerate disease of the nervous system resulting in certain and early death. Onset is in early middle age.

53

Hemophilia
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Sex-linked recessive

Caused by the absence of one or more proteins necessary for normal blood clotting.

54

Color blindness
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Sex-linked recessive

Red-green color blindness

55

Duchenne muscular dystrophy
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Sex-linked recessive

Progressive weakening of muscle control and loss of coordination.

56

Sickle cell disease
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: Autosomal recessive

A mutation in the gene for hemoglobin results in deformed red blood cells. Carriers of the sickle cell trait are resistant to malaria.

57

Down Syndrome
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: 47 chromosomes due to trisomy 21

Characteristic facial features, mental retardation, prone to developing Alzheimers and leukemia.

58

Turner's syndrome
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI:XO 45 chromosomes due to a missing sex chromosome

Small stature, female.

59

Klinefelter's syndrome
WHAT IS ITS PATTERN OF INHERITANCE?

DESCRIBE

POI: XXY 47 chromosomes due to an extra X chromosome

Have male genitals, but the testes are abnormally small and the men are sterile.