biology module 7

during gel electrophoresis, do larger or smaller molecules move faster? explain

smaller molecules of DNA move faster through the gel in gel electrophoresis than larger molecules since they can move more easily. this causes the m to move faster that larger molecules

recombinant DNA

taking DNA from two different species and combining them in one cell

a person carries a genetic disorder but does not have the disorder. how is that possible?

the genetic disorder must be recessive. the person can carry the trait (be a carrier), but as long as he has the dominant allele, the person will not have the disease.

explain the laws of segregation and independent assortment

the laws of segregation states that each parent contributes only one of its two alleles to its offspring- half the parents' gametes carry one allele and half carry the other. the law of independent assortment states that alleles for different traits assort independently of one another during gamete formation

phenotype

the observable expression of an organism's genes

testcross

breeding an organism displaying the dominant phenotype but unknown genotype with a homozygous recessive organism

chromosomal mutations

changes in the chromosomes structure in which a chromosome loses or gains genes during meiosis

sex chromosome

chromosomes that determine the sex of an individual

autosomes

chromosomes that do not determine the sex of an individual

carrier

heterozygotes (individuals with one copy of an allele) for a recessive trait but do not exhibit the trait

what terms do we use to refer to genetic traits that are governed by more than one set of genes?

if a genetic trait is governed by may genes, we call it polygenic inheritance

in fruit flies, the color of the eye is a sex-linked genetic trait. what percentage will have white eyes when a heterozygous red-eye female is crossed with a white-eyed male? what percentage of females will have white-eyes?

if the female is heterozygous then her genotype is X^RX^r. since the male is white-eyed, his genotype is X^rY. thus, 50% of females will be white-eyed (remember on XX are female) and 50% of males ( only XY are male) will be white-eyed.

In the case of the fruit fly eye color again, what must be the genotype of a male fly if, when crossed with a heterozygous female, there is no possibility of having a female with white eyes?

if the male were white-eyed, then the Punnett square would look like the one above, resulting in 50% of the females having white eyes. thus, the males genotype is X^RY

sex-linked inheritance

inheritance of a genetic trait located on the sex chromosome

codominance

inheritance pattern in which heterozygotes express the distinct phenotypes of both alleles

incomplete dominance

inheritance pattern in which heterozygotes have a phenotype intermediate between the phenotypes of the homozygotes

what process causes gametes to have only one allele instead of two alleles for each trait like other human cells?

meiosis separates the two alleles

Two individuals have the exact same genotype for a certain trait, but they are not identical when it comes to that trait. How is this possible?

not all traits are determined completely by genetics. most are also determined by environmental factors. while the genetics are the same, the environmental and spiritual factors were probably different

a pea plant that is homozygous dominant for axial flower allele A is crossed with a pea plant that is heterozygous for that allele. what are the possible genotypes and phenotypes, the phenotypic ratio and the percentage chances for the offspring?

one parent is homozygous dominant, so its genotype is AA. the other heterozygous, so its genotype is Aa. 50% of the offspring have the genotype AA and 50% of the offspring have the genotype Aa. since each offspring has at least one of the dominant allele, however, 100% have the axial flower phenotype. this gives a phenotypic ratio of 1:0

antibody

proteins in your immune system used to attack specific antigens

Do sex-linked genetic disorders affect men and women the same? If not, which sex is affected more and why?

sex-linked disorders affect men more frequently than women. this is because men have only one X chromosome and so need only one allele to display the phenotype

short tandem repeats (STRs)

short sequences of DNA ( usually 2 to 6 base pairs long) that are repeated numerous times at various locations in the noncoding region of a chromosome

give the possible phenotypes, phenotypic ratio, and percentage chance for each offspring in the dihybrid self-fertilization of a pea plant that is heterozygous for smooth, yellow peas.

since the parent with smooth, yellow peas is homozygous. its genotype is SSYY. since the other expresses both recessive alleles, it must be homozygous for the recessive alleles. this, its genotype is ssyy. both of these parents can only produce one type of gamete each. the one parent can only produce gametes with SY alleles and the other can only produce gametes with sy alleles. since there is only one possible genotype, 100% of the offspring have the SsYy genotype and the smooth, yellow phenotype. the phenotype ration is 1:0.

Give the possible phenotypes and the percentage chance for each in the dihybrid cross between pea plant that is heterozygous in producing smooth, yellow peas and another with the same genotype.

since the parents are both heterozygous for each allele, there genotypes are SsYy. there are 4 possible gametes with this combination: SY, Sy, sY, sy. the phenotypic ratio is 9:3:3:1. 9 of 16 or 56.25% of offspring are smooth, yellow peas (SSY, SsYy, SSYy, SsYY). 3 of 16 or 18.75% of offspring are smooth, green peas ( SSyy, Ssyy). 3 of 16 or 18.75 % of offspring are wrinkled, yellow peas (ssYY, ssYy). 1 of 16 or 6.25% of offspring are wrinkled, green peas (ssyy).

if a person has type B- blood, what are the possible genotypes for that person? include the possible genotypes related both to the type of blood as well as the Rh-factor.

since the person is type B, the genotype must be either BB or BO. for the Rh-factor, the person expresses the recessive allele. thus, her genotype must be homozygous for the recessive allele

a woman with type O blood marries a man with type AB blood. what blood types are possible for their children? what is the percentage chance for each blood type?

since the woman is O, her genotype must be OO, as that would be the only way the recessive allele could be expressed. the man is type AB, so his genotype is AB. since the O allele is recessive, the possible blood types for the children are 50% A and 50% B.

a woman is heterozygous for the ability to roll her tongue when extended. if she marries a man who cannot roll his tongue, what percentage of their children will be able to roll their tongues? assume the allele for rolling your tongue is dominant.

since the woman is heterozygous, her genotype is Rr. the man cannot roll his tongue, which is recessive, so his genotype must be rr. since even having one dominant allele allows you to be able to roll your tongue, 50% of the children will be able to roll their tongues

autosomal inheritance

Inheritance of a genetic trait not on a sex chromosome

genotype

Two-letter set that represents the alleles an organism possesses for a certain trait

genome

a complete set of an organism's genetic information encoded in its DNA

monohybrid

a cross between individuals, concentrating on only one definable trait

dihybrid cross

a cross between two individuals, concentrating on two definable traits

homozygous genotype

a genotype in which both alleles are identical

heterozygous genotype

a genotype with two different alleles

what is a plasmid? how is it used as a tool in genetic engineering?

a plasmid is a small circular DNA molecule in bacteria. it is used to carry genes in genetic engineering

gene mutation

a radical change in the DNA of one or more alleles

nondisjunction

a situation in which abnormal cellular events in meiosis lead to either none of a particular chromosome in the gamete or more than one chromosome in the gamete

plasmid

a small circular section of extra DNA that confers one or more traits to a bacterium and can be reproduced separately from the main bacterial genetic code

antigen

a substance that when introduced into the blood, triggers the production of an antibody

use diagram 7.34 to answer the questions that follow. a) describe what is happening at number 1 b) what is the arrow at number 2 pointing to? why is this helpful to the process being shown? c) describe what is happening at number 3 d) what is the final product called?

a) a restriction enzyme cuts the DNA into fragments b) the arrow at number 2 is pointing to one of the sticky ends allow complementary base pairing to occur between the original DNA fragment and a fragment from another source c) a DNA fragment from another source pairs with the fragments of the original DNA d) the new DNA molecule is called recombinant DNA

a DNA profile is shown in figure 7.35. use it to answer the questions that follow. a) explain why there are different DNA fragment lengths ( shorter lengths traveling father than longer lengths) for the victim, sample, and each suspect. b)does the DNA profile indicate that either of the suspects were present at the crime scene? explain

a) restriction enzymes cut each person's DNA at a specific recognition sites. each person will have a different number of nucleotides between recognition sites making different length fragments. no two people( except identical twins) will have the same number of nucleotides between recognition sites b) the DNA profile from Suspect 2 matches the hair sample found on the victim's pants. this suggests that suspect 2 was at the crime scene

what are Mendel's principles of genetics?

a) the traits of an organism are determined by its genes. each gene has alternate forms called alleles b) each organism has two alleles that make up the genotype for a given trait. if the tow alleles are the same the organism is homozygous for that trait. if the two alleles are different the organism is heterozygous for that trait. c) in sexual reproduction each parent contributes ONLY ONE of its alleles to its offspring. the separation of alleles in parents occurs during meiosis - the forming of gametes. this is the known as Mendel's law of segregation. the union of gametes during fertilization reunites allele pairs in offspring d) in each genotype there is a dominant allele. it it exists in an organism the phenotype is determined by that allele

pedigree

A diagram that follows a particular phenotype through several generations

allele

One of a pair of genes that occupies the same position on homologous chromosomes

what is PCR? give an example of its use.

PCR stands for polymerase chain reaction. it is used to make many exact copies of a segment of DNA without the use of cells. it is often used to clone small pieces of DNA from crime scenes so further analysis and comparison are possible

dominant allele

an allele that will determine phenotype if just one is present in the genotype

recessive allele

an allele that will not determine the phenotype unless the genotype with a homozygous recessive organism

restriction enzyme

an enzyme that recognizes and cuts DNA only at a specific sequence of nucleotides

true breeding

an organism that always passes a certain characteristic on to its offspring

transgenic organism

an organism that carries one or more genes from a different species

genetically modified organism (GMOs)

an organism that has been genetically altered by humans