Chapter 14, 15 Flashcards by Allison Dail

Genetics

The study of how characteristics are transmitted from parent to offspring

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Gregor mendel

Austrailian monk who combined science w statistics to study heredity , made laws in 1860s

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Mendels Garden Peas

Pisum sativum; studied 7 traits of pea plants, observed many generations stidying everyones traits,

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What did mendel ensure in his experiment

That he started his experiments w peas that were true breeds

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F1 generation

Offspring of the P generation

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F2 generation

Offspring of the F 1 generation

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Mendels conclusion

Traits are inherited in discrete units (later called genes)

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Allele

An alternative form of a gene

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Law of segregation

Mendels law stating that allele pairs separate during meiosis and end up in different gametes

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Law of independent assortment

Mendels law stating each allele pair segregated independently of other pairs of alleles during gamete formation

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For each of the seven pea characteristics that mendel studied, each pair behaves as if they were on diff chromosomes

Only exception to this rule is if alleles are on the same chromosome
Genes located near each other on same chrom. tend to be inherited together

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Law of segregation and independent assortment result in

Genetic variation

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Carrier

A heterozygous that is phenotypically normal but carries a gene for some trait

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Heterozygote can be more advantageous than homozygous bc has two forms of proteins that may provide functional resilience in response to

Enviornmental stress

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Monohybrid cross

Cross between individuals that involves one pair of contrasting traits

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Punnett square

Diagram hat predicts the gentic outcome of diff types of crossed

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Test cross

Used to determine the genotype of an unknown individual

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To do a testcross

Cross unknown to a homozygous recessive and analyze offspring

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Dihybrid cross

Cross between invidividuals that involves two pairs of contrasting traits

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Rule of multiplication

Math way to determine chance of 2+ independent events happening simultaneously

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Incomplete dominamce

When intermediate phenotype is formed like pink flower (Rr)

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Codominance

Lizard w yellow and blue spots

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Multiple allele traits

ABO blood groups controlled by 3+ alleles of same gene

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Polygenic inheritance

Skin color controlled by 2+ genes

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Nonnuclear inheritance

Inheritance of genetic info from sources other than the chromosomes or dna in nucleus

CF (ff) autosomal recessive

Protein in membrane is defective or absent so chloride ions cant pass to outside of cell, chloride ions accumulate in cell which leads to buildup of mucus

Symptoms of cf

Mucus buildup in pancreas lungs digestive tract or other organs leading to poor absorption of nutrients, chronic bronchitis, and recurrent bacterial infections

Tay-Sachs disease (tt) autosomal recessive

An enzyme that metabolizes lipids in the brain doesnt function properly so lipids accumulate in the brain

Symptoms of tay sachs

Seizures, blindness, gradual deterioration of brain tissue leading to a loss of motor and mental ability

Tay sachs affect individuals

Usually die in early infancy

Sickle cell anemia (aa) autosomal recessive

Caused by a substitution of the wrong amino acid in hemoglobin protein, which causes the hemoglobin to be the improper shape amd often clump together

Symptoms of sickle cell

Misshaped red blood cells lead to impaired blood circulation and organ damage

Huntingtons disease (H_) autosomal dominant

Symptoms dont appear until 30-40, if you have it one of your parents had it

Symptoms of huntingtons disease

Deterioration of the central nervous system

Phenylketonuria (PKU) autosomal recessive (pp)

Cant properly break down the amino acid phenylalanine which accumulates to toxic levels in the blood caisimg improper development of the brain

How is PKU overcome

By regulating the diet

Hemophilia (X^h Y or X^h X^h)

X linked recessive disease that is much more common in men

Symptoms of hemophilia

Blood can't clot

In the early 1900s Thomas Hunt Morgan worked w ________ (fruit flies) and confirmed mendels idea that genes are located at specific locations on chromosomes

Drosophilia

Morgan's discoveries

X/Y chrom are responsible for determining sex | There are genes on sex chromosomes which led to his discovery of SEX LINKAGE

Linked genes

Genes located on the same chromosome

Linked genes tend to be what

Inherited together bc the chrom is passed on as a unit unless crossing over

Genetic map

Diagram showing the location of genes on a chromosome

The frequency of crossing over between 2 linked genes is proportional to the distance between them

Map unit

Used to determine the probability that crossing over between genes will occur

Genes that split up due to crossing iver 1% of the time are

1 map unit apart

Sex is determined by what chromosome

23rd chromosome in the male gamete (sperm)

Grosshoppers

X-O system Male is X Female is XX

Birds

Z-W system Male is ZZ Female is ZW

Bees

No sex chromosomes Male has 16 (haploid) Female has 32 (diploid)

X linkedtraits (sex linked)

Genes Located on the X chromosome

Example of X-linked traits

Color blindness, muscular dystrophy, hemophilia

Sexlimited trait

Genes that are present in both sexes but are expressed in only one sex and remain turned off and the other sex

Why are sex limited traits the way they are

Often due to the presence or absence of sex hormones

Example of sex limited trait

Male pattern baldness | Milk production in females

Barr body

An in active X chromosome that is normally found in the nucleus of somatic cells of a female

Nondisjunction

When chromosomes failed to separate during meiosis | Causing 22 or 24 chromosomes

Monosomic

A zygote that is lacking a chromosome (45)

Trisomic

Zygote that contains one extra chromosome (46)

Polyploidy

A chromosome alteration in which the organism possesses more than two chromosome sets

Polyploidy also called

Gene duplication Much more common in plants Can lead to evolution of the function of the new gene

Karyotype

A picture of a persons chromosomes

Down syndrome

Having an extra 21st chromosome

Klinefelters syndrome

Males with an extra X-chromosome (xxy) | Symptoms: male sex organs amd female characteristics, usually sterile

Turner syndrome

Females that have only one X chromosome (XO) | Symptoms: sex organs dont develop akd secondary sex characteristics fail to develop