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chapter 11
chapter 11
50
Biology
10th Grade
01/06/2010

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Term
genetics
Definition
the scientific study of heredity
Term
gregor mendel
Definition

experimented w/ pea plants to understand heredity

he knew that:

-male part of each flower produces pollen (sperm)

-female part of each flower produces egg cells

he wanted to produce seeds by joining male and female reproductive cells from 2 diff plants. he cut away the pollen bearing male parts of the plant and dusted the plants flower with pollen from another plant. he was able to produce seeds that had 2 diff parents. 

Term
cross- polination
Definition
Mendel cut away the pollen bearing male parts of the plant and dusted the plants flower with pollen from another plant. this process is called cross polination
Term
fertilization
Definition
a process during sexual reproduction when the male and female reproductive cells join. fertilization produces a new cell. 
Term
self pollination
Definition
the seeds that are produced from self pollination inherit all of their characteristics from the single plant that bore them 
Term
true breeding
Definition
mendel had true breeding pea plants that, if allowed to self pollinate, would produce offspring identical to themselves
Term
trait
Definition
a specific characteristic that varies from one individual to another
Term
P generation
Definition
parent generation. original pair (of plants in mendels case)
Term
F1 generation
Definition
first filial generation- offspring
Term
hybrid
Definition
offspring of crosses between parents with different traits
Term
genes
Definition
factors that determine traits and are passed from one generation to the next
Term
alleles
Definition
different forms of a gene
Term
principle of dominance
Definition
states that some alleles are dominant and others are recessive. an organism with a dominant allele for a trait will always exhibit that trait and organisms with recessive alleles for traits will only exhibit the traits when that dominant allele is not present. 
Term
segragation
Definition
the reappearance of the trait controlled by the recessive allele indicated that at some point the allele for shortness had been separated, or segregated, form the allele for tallness
Term
gametes
Definition
mendel suggested that the alleles for tallness and shortness in the F1 plants segregated from each other during the formation of the sex cells, also called gametes
Term
what does the F1 generation produce?
Definition
when each F1 plant flowers and produces gametes, the two allele segregate from each other so that each gamete carries only a single copy of each gene. therefore, each F1 plant produces two types of gametes- those with the allele for tallness and those with the allele for shortness. 
Term
punnett square
Definition
the gene combinations that might result from a genetic cross can be determined by drawing a diagram called a punnett square. predict and compare the genetic variations that might result from a cross (capital letter= dominant allele, lowercase letter = recessive allele)
Term
homozygous
Definition
organisms that have two identical alleles for a particular trait (true breeding)
Term
heterozygous
Definition

organisms that have two different alleles for a particular trait (hybrid)

 

Term
phenotype
Definition
physical characteristics
Term
genotype
Definition
genetic makeup
Term
independent assortment
Definition
principle states that genes for different traits can segregate independently during the formation of gametes. independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms. 
Term
summary of mendels principles
Definition

- genes are passed from parents to offspring

- if two or more alleles of the gene for a single trait exist, some forms of the gene may be dominant and others recessive

- in most sexually producing organisms, each adult has 2 copies of each gene. these genes are segregated from each other when gametes form

- alleles for different genes usually segregate independently of one another

Term
are all alleles dominant or recessive?
Definition
no! many traits are controlled by multiple alleles or multiple genes
Term
incomplete dominance
Definition

when one allele is not completely dominant over another. the heterozygous phenotype is between the 2 homozygous phenotypes.

red + white= pink (phenotype blends)

Term
codominance
Definition
when both alleles contribute to the phenotype. phenotype doesn't blend phenotypes like incomplete dominance but just shows both. 
Term
multiple alleles
Definition
genes that are controlled by more than two alleles are said to have multiple alleles (individual can't have more than 2 alleles but a population can)
Term
thomas hunt morgan
Definition
used fruit flies to advance study of genetics. decided mendels prinicples applied to all organisms. 
Term
does interaction between genes and the environment help determine the characteristics of any organism?
Definition
yes!
Term
polygenic traits
Definition
traits controlled by two or more genes 
Term
mendels principles required two things:
Definition

1. each organism must inherit a single copy of every gene from its "parents"

2. when an organism produces its own gametes, those 2 sets of genes must be separated from each other so that each gamete contains just one set of genes 

Term
homologous
Definition
the 2 sets of chromosomes are homologous, meaning that each of the 4 chromosomes that came from the male parent has a corresponding chromosome from the female parent
Term
diploid
Definition
a cell that contains both sets of homologous chromosomes (2N=8). contain 2 complete sets of chromosomes and 2 complete sets of genes. 
Term
haploid
Definition
gametes of sexually reproducing organisms contain only a single set of chromosomes thus one set of genes (N=4)
Term
Meiosis
Definition
a process of reduction division in which the number of chromosomes per cell is cut in half thru the separation of homologous chromosomes in a diploid cell (includes meiosis I and II). by the end of meiosis II the diploid cell that entered meiosis has become 4 haploid cells unlike mitosis
Term
Interphase I
Definition
cells undergo a round of DNA replication, forming duplicate chromosomes
Term
Prophase I
Definition
each chromosome pairs with its corresponding homologous chromosome to form a tetrad. 4 chromatids in a tetrad. when homologous chromosomes form tetrads in meiosis I, they exchange portions of their chromatids in crossing over- produces new combos of alleles
Term
Metaphase I
Definition
spindle fibers attach to the chromosomes
Term
Anaphase I
Definition
the fibers pull the homologous chromosomes toward opposite ends of the cell
Term
telophase I and cytokenesis
Definition
nuclear membranes form. cell separates into 2 which have chromosomes and alleles that are different from each other and from the diploid cell that entered meiosis I
Term
Meiosis II
Definition
no replication. each of the cell's chromosomes has 2 chromatids
Term
Prophase II
Definition
meiosis I results in 2 haploid daughter cells, each with half the number of chromosomes as the original cells
Term
Metaphase II
Definition
the chromosomes line up in the center of the cell
Term
anaphase II
Definition
sister chromatids separate and move toward opposite ends of the cell
Term
telophase II and cytokenesis
Definition
results in 4 haploid daughter cells
Term
gamete formation
Definition
in male animals meiosis= 4 equal sized gametes aka sperm. in females only one egg results (other 3 called polar bodies, arent involved)
Term
linkage
Definition
each chromosome is a group of linked genes so chromosomes, not genes, assort independently
Term
alfred sturtvent said...
Definition
the farther apart 2 genes were, the more likely they were to be seperated by cross over in meiosis. created gene map that showed locations of each known gene on one of the Drosophila chromosomes. if 2 genes close together, recombination frequency between them is low cuz crossovers are rare. if far apart its high. 
Term
meiosis vs. mitosis
Definition
mitosis results in production of 2 genetically identical diploid cells and meiosis produces four genetically different haploid cells 
Term
principle of genetics
Definition
can be used to study inheritance of human traits and to calculate the probability of certain traits appearing in the next generation
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