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bio > Chapter 8: Genetics > Flashcards

Chapter 8: Genetics Flashcards

1
Q

Genetics

A

Study of the transfer of genes from parents to offspring

The nature in nature vs nurture

Genotype is an organism’s genetic makeup

Phenotype is how genes are expressed

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2
Q

Animal Breeding

A

Humans have understood for centuries that parents pass traits to offspring

Through domestication humans selectively bred individuals for desired traits

Docility, intelligence, strength, coat quality, fat content, milk production, appearance

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3
Q

Genetics: What are Genes?

A

Nucleus holds chromosomes

Chromosomes are made of DNA

Pairs of chromosomes

Genes are segments of DNA

Code for specific proteins, control biochemical processes

Blueprint of life

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4
Q

DNA

A

Deoxyribonucleic acid
Double strand of nucelotides= deoxyribose sugar, phosphate, nitrogenous base

Purines- adenine (A) and guanine (G)

Pyrimidines- thymine (T) and cytosine ©
A to T and G to C

Genes are made of sequence of base pairs

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5
Q

Genome

A

Genome is all the genes for an organism

Different species have different numbers of chromosomes, genes

DNA must be supercoiled to fit thousands of genes per chromosome

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6
Q

Somatic Cells

A

Somatic cells- body cells have 2 pairs, diploid (2n)

Humans- 46, 23 pairs

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7
Q

Gametes

A

reproductive cells 1 pair, haploid (n)

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8
Q

Sex Chromosomes

A

have genes related to sex characteristics, Autosomes- everything else

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9
Q

Sex Determination

A

In mammals males are XY (sperm), females are XX (egg)

In chickens females are ZW, males are ZZ

Crocodilians, turtles temperature dependent

Amphibians, fish lots of forms of determination

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10
Q

Chromosome Number

A

Expressed as n, Varies widely

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11
Q

Polyploidy

A

more than 2 copies of chromosomes, or whole genome

Mistake during cell division

Not common in vertebrates, widespread in plants, can cause low seed production

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12
Q

Aneuploidy

A

variation in number of individual chromosomes

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13
Q

Monosomic

A

one less (2n-1)

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14
Q

Trisomy

A

one more (2n+1)

Often lethal, sometimes not.

Down’s syndrome caused by Trisomy of chromosome 21

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15
Q

DNA Replication

A

Must be accurate to prevent mistakes in offspring

DNA molecule unzips, RNA primer attaches to DNA polymerase

Polymerase moves down original strand

Bonds new nucleotides together to original strand, polymerization

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16
Q

DNA Replication: When do we do it?

A

Anytime body cells (somatic cells) divide

Growth, injury, maintenance

Anytime sex cells (gametes; sperm, eggs) divide

Reproduction

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17
Q

Mitosis

A

Somatic cell division, produces two 2n cells- 2 copies of chromosomes

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18
Q

Meiosis

A

Reproductive cell division, produces 4 n cells-1 copy of chromosomes

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19
Q

Principle of Inheritance

A

1866 Gregor Mendel discovered principles of inheritance while studying pea plants

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20
Q

Alleles

A

forms of a given gene, each creates different proteins, so express traits differently, get one copy from each parent

Chromosomes in homologous pairs, genes for the same traits

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21
Q

Locus

A

is a certain spot on chromosome

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22
Q

Animals with matching alleles at a locus

A

Homozygous, (AA or aa) different alleles are Heterozygous (Aa)

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23
Q

Inheritance

A

is passing of alleles in gametes

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24
Q

gamete production

A

pairs separate

25
Q

Law of Segregation

A

alleles separate so only one per gamete

26
Q

Law of Independent Assortment

A

separation of a pair of genes is independent of separation of other pairs

27
Q

Gene Expression: Complete Dominance

A

Dominant alleles mask recessive alleles and are expressed over them, signify dominant allele with capital letter

EE colored coat, ee white, Ee colored

EE is the genotype, colored is the phenotype

28
Q

Punnett Square

A

Used to predict the results of a genetic cross

In a genetic cross, two parents (P generation) are crossed to produce offspring (F1 generation).

The simplest Punnett square follows one
character in a monohybrid cross.

29
Q

Test Crossing

A

Can’t always tell genotype by looking at phenotype

Can test cross individual with homozygous recessive to see what offspring are

If some recessive, then parent is heterozygous

30
Q

Codominance

A

neither allele masks the other, both are expressed
Red coat (RR) + white coat (WW) = roan (RW)

31
Q

Incomplete dominance

A

heterozygous individual is intermediate

32
Q

Epistasis

A

expression of one gene is influenced by the presence of another
Defies classical Mendelian genetics

Horse hair color black is E at E locus, but whether black all over or just points is controlled by another locus

Ea is black, EA is bay with black points

33
Q

Multiple alleles

A

only 2 alleles on each locus, but population could have many alleles

A-B-O blood types in humans

34
Q

Polygenic inheritance

A

is the effect of many genes on a single character.

In humans, height and skin color are each affected by several genes.

Size and growth rates common in animals

35
Q

Sex-Linked Inhertiance

A

Some genes only found on X or Y, homologous in some regions, not in others

X-linked genes can be inherited by males and females

Y-linked only in males

Found on autosomes, phenotypes are not expressed the same way for the sexes

In male sheep horns (H) is dominant to polled (no horns(h)), in females h is dominant

So heterozygous male has horns, hetero female doesn’t

36
Q

Sex-Limited Traits

A

Traits unique to a single sex

Milk production, egg production

Both have genes, but only one sexes expresses them

37
Q

Gene frequency

A

proportion of a particular allele in a population

38
Q

Genotypic frequency

A

how often a genotype occurs in a population

39
Q

Phenotypic frequency

A

how often a phenotype occurs in a population

40
Q

Animal breeding

A

uses pop genetics to improve livestock

41
Q

Mutations

A

changes in the composition of a gene that alter DNA, producing new alleles

Mutations that affect phenotype are rare

Beneficial ones spread through natural selection

42
Q

Genetic drift

A

change in gene frequency due to chance, affected by population size

Big problem for small populations

43
Q

Migration

A

wild animals migrating or bringing new breeding stock into a population

Can make large changes in gene frequencies quickly this way

Works best when new sire is very different from herd

44
Q

Selection

A

allowing some animals to breed more than others

45
Q

Natural Selection

A

some individuals are better adapted and will therefore breed more

Happens in managed herds with multiple bulls

Wild populations

46
Q

Artificial selection

A

breeding controlled by manager, culling less desirable animals

Affected by rate of reproduction and generation time

47
Q

Hardy-Weinberg Law

A

In a large, randomly mating population without natural selection, migration, or mutation, gene frequencies will remain stable

Rare in the wild, common in managed herds

Once desired genes are achieved in a large herd, they will remain constant

48
Q

Qualitative traits

A

phenotypes classified into groups

Coat color, horn presence

49
Q

Quantitative traits

A

numerically measured, usually polygenic

Growth rate

Additive gene action- no dominance at locus, each gene increases the effect

A+ gene makes calves 2lbs heavier at birth, AA is norm, A+A+ is 4lbs heavier

50
Q

Nature vs. Nurture

A

Genes determine your potential, but environment determines if live up to that potential

Climate, management practices, health

51
Q

Heritability

A

How much phenotypic variability among individuals that is due to genetics and can be passed down

Ranges from 0-1

First calculate a selection differential- difference between the population and desired trait, multiply by heritability value

Need to be considered before breeding

Pig litter size- norm is 7, breed parents from litters of 11

Differential is 11-7= 4

Heritability value is .1, so 4x.1= .4

So litter will be 7.4 piglets larger

Some traits are more heritable than others

52
Q

Relationship Coefficient

A

Measures how closely related individuals are, also important before breeding.

Ranges from 0-1
Parent-offspring- 0.5
Siblings- 0.5
Half-Siblings- 0.25
Grandparent-offspring- 0.25

53
Q

Inbreeding

A

mating closely related individuals

Increases homozygosity, decreases genetic variation

Can increase incidence of detrimental recessive traits

Causes decline in quality called inbreeding depression

54
Q

Linebreeding

A

inbreeding to concentrate genes of an outstanding ancestor

Genetic evaluations have eliminated need for this in livestock, but still practiced in companion animals

55
Q

Outbreeding

A

mating less closely related individuals

Increases heterozygosity, genetic diversity

Increases vigor, known as heterosis

Lowly heritable traits show more heterosis

56
Q

Crossbreeding

A

mating animals of different breeds

Most successful if parent genetics complement each other

Strengthen good traits, depress bad ones

Great for reproductive traits

Often breed crossbred mothers with purebred sires

Tend to be more vigorous, fertile, and healthy

57
Q

Biotechnology

A

Tools that use living organisms to make improvements or modifications for specific uses

58
Q

Genetic engineering

A

altering an animals genes

59
Q

Transgenic Organisms

A

Bacteria that produce human insulin

Before used pig and cattle insulin, slightly different

Cows, sheep, goats can produce proteins in milk to treat disease

Can produce large quantities

Chickens can produce proteins in eggs

Animal models for human diseases
Animals to produce organs for human transplant

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