Ch. 9 Patterns of Inheritance Flashcards Preview

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Flashcards in Ch. 9 Patterns of Inheritance Deck (55):
1

Genetics

Science of heredity (study of the inheritance of traits)
- founded by Gregor Mendel

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Who was Gregor Mendel?

"Father of Genetics"
- experiment with pea plants for seed shape, color (flower/seed), pod shape, flower position, stem length plant mating
- parents pass onto offspring discrete heritable factors that retain individuality generation to generation

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Chromosome Theory of Inheritance

Genes are physical units located on chromosome and the behavior of chromosomes during meiosis/fertilization determine inheritance patterns

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Mono-hybrid cross

Cross w/ only 1 variable at a time

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Allele

Alternative form of a gene
- each trait is determined by 2 alleles (1 from each parent)

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Dominant

Allele that rules/dominates over other
- expressed (A)

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Recessive

Hidden/masked by dominant allele
- expressed w/ 2 recessive alleles (a)

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Genotype

Genetic description a trait based on a pair of alleles (BB)

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Phenotype

Physical appearance/description of a trait

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Homozygous

Genotype w/ same pair of allele (purebred)

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Heterozygous

2 different types of alleles in genotype (hybrid)

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Parental Cross

Pure dominant crossed with pure recessive

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Principle of Segregation

Pairs of alleles separate during gamete formation

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Principle of Independent Assortment

Each pair of alleles separate independently during gamete formation

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Dihybrid cross

Genes fro two traits are independent

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Probability

Mathematical science that predicts the chance a certain event will occur

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Rules of multiplication

The change that two independent events will occur together is the product of their chances occurring separate

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Does chance have memory?

No. A change event is not affected by previous events.

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Trihybrid Cross

3 traits at the same time

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Wild type

The phenotype most commonly found in nature

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Self-fertilization

Fusion of sperm and egg that are produced by the same individual organism

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Cross fertilization

Fusion of sperm and egg derived from two different individuals

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Hybrids

The offspring of parents of two different species or of 2 different varieties of 1 species
- the offspring of 2 parents that differ in 1+inherited traits
- an individual that is heterozygous for 1+ pairs of genes

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Cross (hybridization)

Cross fertilization of 2+ different varieties of an organism or of 2 different species

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P Generation

Parent individuals from which offspring are derived in studies of inheritance

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F1 Generation

Offspring of 2 parental (P Gen) individuals

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F2 Generation

Offspring of the F1 gen

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What are the 4 hypothesis of Mendel?

1) There are alternative forms of genes, the units that determine heritable traits
2) For each inherited characteristic, an organism has two genes, one from each parent. These genes may both be the same allele, or they may be different alleles
3) A sperm or egg carries only 1 allele for each inherited trait, b/c allele pairs separate (segregate) from each other during the production of gametes, and each contribute an allele to offspring
4) when the two genes of a pair are different alleles and one is fully expressed while the other has no noticeable effect on the organism's appearance.

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Punnet Square

A diagram used in the study of inheritance to show the results of random fertilization

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Test Cross

The mating b/w an individual of unknown genotype for a particular characteristic and an individual that is homozygous recessive for that same characteristic

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Rule of Addition

The probability that an event can occur in two+ alternative ways is the sum of the separate probabilities of the different ways

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Which is more common? Recessive or dominant?

Recessive

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Carriers

An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder

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Cystic Fibrosis

A genetic disorder that occurs in people w/ 2 copies of a certain recessive allele characterized by an excessive secretion of mucus and consequent vulnerability to infection
- common for European ancestry
- probability increases with close relative mating

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Achondroplasia

A form of human dwarfism caused by a single dominant allele

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Huntington's Disease

Human genetic disorder caused by a dominant allele characterized by uncontrollable body movements and degeneration of nervous system

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Amniocentesis

A technique for diagnosing genetic defects while a fetus is in the uterus
- a sample of amniotic fluid, obtained via a needle inserted into the union is analyzed for telltale chemicals/defective fetal cells
- 14 to 16 week

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Chorionic villus sampling

A technique used for diagnosing genetic defects while the fetus is in the uterus
- a small sample of the fetal portion of the placenta is removed and analyzed
- 8 to 10 week

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Ultrasound Imaging

A technique for examining a fetus in the uterus
- high frequency sound waves choking off the fetus are used to produce an image of the fetus
- 18 week

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Fetoscopy

A technique for examine a fetus for anatomical deformities
- a needle-thin containing a viewing scope is inserted into the uterus, giving a direct view of the uterus

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Incomplete Dominance

A type of inheritance in which the phenotype of a heterozygote is intermediate b/w the phenotypes of the 2 types of homozygote

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Why is relationship of genotypes to phenotypes rarely simple?

No complete dominance, 2+ alternative alleles for gene, genotype doesn't always indicate phenotype

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ABO blood groups

3 alleles produce 4 phenotypes (A, B, O, AB)

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Codominance

Expression of 2 different alleles of a gene in a heterozygote

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Pleiotropy

The control of more than 1 phenotypic characteristic by a single gene
- ex. sickle cell

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Genetic screening

Testing people for alleles associated w/ a particular genetic disorder

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Polygenic inheritance

The additive effect of 2+ gene loci on a single phenotypic characteristic
- ex. skin color

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Recombination frequency

w/ respect to 2 given genets, the # of recombinant progeny from a mating divided by the total # of progeny
- carry combinations of alleles different from those in either of the parents as a result of independent assortment of chromosomes or crossing over

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Sex Chromosome

A chromosome that determines whether an individual is male or female
- XX, XY

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Monoecious

Having individuals that produce both sperm and eggs (usually refers to plants)

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Hermaphroditic

A condition in which an individual has both female and male gonads and functions as both a male and female in sexual reproduction by producing both sperm and eggs (animals)

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Sex-Linked Gene

A gene located on a sex chromosome

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Red green color blindness

A category of common, sex-linked human disorders involving several genes on the X chromosomes
- characterized by a malfunction of light-sensitive cells in the eyes
- affects mostly males but also homozygous females

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Hemophilia

A human genetic disease caused by a sex-linked recessive allele, characterized by excessive bleeding following injury.

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Duchenne muscular dystrophy

A human genetic disease caused by a sex-linked recessive allele
- characterized by progressive weakening and a loss of muscle tissue