Biology Chpt. 7.1-7.3

Front 1

allele

Back 1

each of the 2 copies of the gene

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inheritance of genes

Back 2

-humans have 23 pairs of chromosomes (46 individual chromosomes) and thus 2 copies of each gene
-each human gamete has just 1 copy of each chromosome and thus 1 copy of each gene
-child inherits 1 set of chromosomes from each parent and, thus 2 copies of each gene

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heredity

Back 3

offspring resemble their parents more than they resemble other random people in the universe- passing of characteristics from parents to offspring through their genes

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single-gene traits

Back 4

traits that are determined by the instructions a person carries on one gene - traits exhibit straightforward patterns of inheritance

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pre-made human (Mendel)

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mistaken idea that a tiny, pre-made human existed in every sperm cell was introduced in the 1600s - theory remained popular through the 1800s.

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mendel experiment #1

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studied the garden pea; relatively easy to fertilize (manually by pollen dusting), easy to collect dozens or hundreds of offspring from a single cross (male pollen is used to fertilize female eggs), and fast enough breeders that Mendel could conduct experiments that lasted for multiple generations

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mendel experiment #2

Back 7

chose to focus on easily categorized traits; shape - all peas of the variety that mendel studied were either round or wrinkled in shape, with nothing in between. &all peas are either yellow or green in color, no shades. looked at 7 different traits but each trait only 2 various ever appeared

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mendel experiment #3

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breeding together similar plants until he had many distinct populations, each of which was unvarying for a particular trait. true-breeding round pea plants always produced plants with round peas when they were crossed together, same with all the other traits (now can set up all the different crosses)

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true-breeding

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they always produced offspring with the same variant of the trait as the parents

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Mendel's cross-breeding

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crossed plants with different traits (green peas and yellow) always resulted in yellow peas - devised a hypothesis that would explain his observations and generate predictions about the outcome of further crosses

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dominant and recessive

Back 11

dominant trait masks the effect of a recessive trait when an individual carries both the dominant and recessive versions of the instructions for the trait

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dominant and recessive #1

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rather than passing on the trait itself, each parent puts into every sperm or egg it makes a single set of instructions for building the trait (today called a gene)

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dominant and recessive #2

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offspring receive 2 copies of the instructions for any trait

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homozygous

Back 14

an individual inherits the same 2 alleles - this is what genotype is called - shows the trait specified by the instructions embodied in those alleles

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heterozygous

Back 15

an individual inherits a different allele from each parent - this is what genotype is called; if one of the alleles is fully apparent in the individual while the other is not, the first is called the dominant allele and is said to "mask" the effect of the other allele, which is the recessive allele

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Mendel's law of segregation

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only 1 of the 2 alleles for a gene is put into a gamete; at fertilization, offspring receive from each parent one allele for each gene- those ones are significant and important enough

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phenotype

Back 17

the outward appearance of an individual - includes features visible to the naked eye such as height, or antlers - includes less easily visible characteristics such as chemicals and individuals produces to clot blood or digest lactose

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genotype

Back 18

an organism's genetic composition - speak of it in reference to a particular trait

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Punnett square

Back 19

useful tool for determining the possible outcomes of a cross between 2 individuals - helps determine organisms' genotypes

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probability

Back 20

plays a central role in genetics - in segregation, each gamete that an individual produces receives only 1 of 2 copies of each gene the individual carries in its other cells, but its impossible to know which allele goes into the gamete (depending on hetero/homo, multiply the 2 components together to determine overall probability

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chance's role

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plays a role in fertilization, too: all of the sperm or eggs produced by an individual are different from one another, and any one of those gametes may be the gamete involved in fertilization

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test-cross

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you take an individual exhibiting a dominant trait, but whose genotype is unknown - you cross (mate) that individ. with an individ. that is homo recessive and look at the phenotypes of their offspring

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pedigree

Back 23

a type of family tree that can help answers such as - genetic disease carriers, recessive/dominant, carried on sex chromosomes?

Front 24

pedigree set up

Back 24

start @ bottom, each row represents a generation, listing all children in order of birth - all the way to parents' parents and as far as it can go (squares=males, females=circles)

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sex-linked traits

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traits that are controlled by genes on the sex chromosomes - recessive ones appear more frequently in males, dominant ones appear more frequently in females

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carrier

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an individual who carries one allele for a recessive trait, and so does not exhibit the trait but can have offspring that do

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incomplete dominance

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the heterozygote appears to be intermediate between the 2 homozygotes (flower color of snapdragons)

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codominance

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the heterozygote displays characteristics of both homozygotes - alleles can be thought of as codominant because neither masks the effect of the other - occurs with sickle cell disease

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sickle cell disease

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-HbA HbA (homozygote) does not have sickle cell disease
-HbS HbA (heterozygote) individual carries a defective allele and has an intermediate condition, some cells become sickled under extreme conditions
-HbS HbS (homozygote) individual has 2 copies of the defective hemoglobin allele and has sickle-cell disease

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multiple allelism

Back 30

a single gene has more than 2 alleles - occurs when there are 3 or more alleles for a gene within a population. an individual still inherits only 2 alleles, one from each parent

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ABO blood groups

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-A and B - completely dominant to O
-blood type A genotype AA or AO
-blood type B genotype BB or BO
-carry 2 copies of O, you are O blood type
-A and B are codominant so blood type AB is possible
(3 allele in populations, but 4 different blood types - A, B, AB, O

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antigens

Back 32

chemicals on the surface of some cells; act as signposts that tell the immune system whether the cell belongs in the body; antibodies are immune system molecules that attack cells with foreign antigens

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blood donation

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-type A; donate to A, AB; receive from A, O
-type B; donate to B, AB; receive from B, O
-type AB; donate to AB; receive from A, B, AB, O
-type O; donate to O; receive from O

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polygenic

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for humans and most animals - height is influenced by many different genes - also skin color and eye color

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additive effects

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describes what happens when the effects of alleles from multiple genes all contribute to the ultimate phenotype

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pleiotropy

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some individual genes can influence multiple unrelated traits; an allele that causes cells to sickle has 2 effects: it disrupts red blood cell's oxygen delivery and it causes red blood cells to be inhospitable to malarial parasites

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SRY gene

Back 37

sex-determining region on the Y chromosome - causes fetal gonads to develop as testes shortly after fertilization - other developmental changes occurs, such as developmental of the internal and external male reproductive structures; also responsible for behavioral characteristics

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sex-linked traits: color-blindness

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a sex-linked trait is carried on the X chromosome; women carry 2 copies of the X chromosome, while men carry an X chromosome and Y chromosome

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to be color-blind

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male must inherit color-blindness allele (r) from his mother, female must inherit color-blindness allele from both parents

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to have normal vision

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male must inherit normal color-vision allele (R) from his mother; female can inherit normal color-vision allele (R) from either her mother or father

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genotypes and phenotypes

Back 41

genotypes are not like blueprints that specify phenotypes; phenotypes are generally a product of the genotype in combination with the environment.