Exam 4 - BIO140

what did Gregor Mandel do

Laid groundwork for chromosome theory of inhesritance through series of experiments on garden peas

what did Sutton and Boveri do

they proposed chromosome theory of inheritance

the branch of biology that focuses on inheritance

Genetics

transmission of traits from parents to offspring

Heredity

any observable characteristic of an individual

trait

what are the two hypothesis of inheritance that were proven to be false

Blending inheritance = Parental traits blend so that their offspring have intermediate traits and inheritance of acquired characteristics = parental traits are modified through use and then passed on

model organisms

non human organisms used for research, practical to work with, conclusions drawn from them can be applied to other species

Peas self-fertilize meaning

Male organs produce pollen grains, which make sperm, female organs produce eggs, flower’s pollen falls on female organ of the same flower

using pollen from one flower to fertilize another is called

cross fertilization

what are pure lines

lines that produced offspring identical to themselves when self- fertilized

The patterns of inheritance of any genes not on a sex chromosome that are the standard patterns of inheritance are called

autosomal inheritance

what was the earliest gene definition

A hereditary factor that influences a particular trait

what is the modern definition of a gene

a region of DNA in a chromosome that codes for a particular protein or RNA

A particular form of a gene

allele

A listing of the alleles of particular genes in an individual

genotype

An individual’s observable traits

phenotype

having two of the same alleles

homozygous

Having two different alleles

heterozygous

An allele that produces its phenotype in heterozygous and homozygous genotypes

dominant allele

An allele that produces its phenotype only in homozygous genotypes

recessive allele

Hybrid

Hybrid Offspring from crosses between homozygous parents with different genotypes (Hybrids are heterozygous)

A trait that appears commonly in two or more different forms.

Polymorphic Trait

A cross in which the phenotypes of the male and female are reversed compared with a prior cross

reciprocal cross

A cross of a homozygous recessive individual and an individual with the dominant phenotype but unknown genotype.

test cross

genes found on either sex chromosome (X or Y)

sex linked genes

Refers to a gene located on the X chromosome or a trait associated with a gene on the X chromosome and skips a generation

x- linked

 Referring to a gene located on the Y chromosome or a trait associated with a gene on the Y chromosome

y - linked

what is a monohybrid cross

Mating between parents that each carry two different genetic determinant for the same trait

example of a monohybrid cross

crossing plants with round seeds and plants with wrinkled seeds: All offspring had round seedsp

what is the principle of segregation

two members of each gene pair must seperate and they separate into different gamete cells during formation of eggs and sperm in parents

Mendel’s model explained the results of a monohybrid cross (5 claims)

Peas have 2 copies of each gene and thus may have two different alleles of the gene, Genes do not blend together, each gamete contains one copy of each gene (one allele), each parent contributes equally to the genotype of their offspring, some alleles are dominant to other alleles. (heterozygous has dominant phenotype)

Two hypothesis for assortment

Independent assortment = Alleles of different genes are transmitted independently of each other. (mendel’s result supported this). Dependent assortment = The transmission of one allele depends on the transmission of another

what is the chromosome theory of inheritance

It arose out of Sutton and Boveri’s observations of meiosis where genetic information is transmitted from one generation to the next, Genes are located on chromosomes at a particular locus

Genes for different traits assort independently of one another at meiosis because

They are located on different nonhomologous chromosomes and they assort independently of one another

phenotype associated with dominant allele appeared heterozygous

complete dominance

Simultaneous expression of phenotype associate with each of the alleles in heterozygote

codominance

Heterozygotes have an intermediate phenotype meaning they have

incomplete dominance (Rr)

Homozygous or heterozygous individuals have dominant phenotype so the trait is

autosomal dominant

Each DNA strand consists of deoxyribonucleotides which have

Deoxyribose sugar, phosphate group, and nitrogenous base

deoxyribonucleotides link together to form polymers of DNA through

phosphodiester linkages which are covalent bonds

how do deoxyribose link

 Hydroxyl group on 3’ carbon of one deoxyribose joined by covalent bond to phosphate group attached to 5’ carbon of another deoxyribose

Two DNA strands line up in opposite direction to each other in antiparallel fashion and antiparallel strands twist to form double helix was proposed by

Watson and Crick

what are the complementary base pairing in DNA

G hydrogen bonds with C, A hydrogen bonds with T

Double-helical DNA is stabilized by

complementary base pairing and interaction between stacked base pairs inside helix

what is the name of the replication that parental strands separate, and each is template for new daughter strand so each daughter has one old and one new strand

semiconservative replication

the two hypothesis about DNA synthesis that were proven wrong were

Conservative replication = Parental molecule serves as an entirely new molecule: One daughter has both old strands; other has both new strands. Dispersive replication = Parent molecule is cut into small pieces, Each daughter has old and new DNA interspersed.

Enzyme that catalyzes DNA synthesis

DNA polymerase

DNA always proceeds in what direction?

5’→3’ because DNA polymerases can add deoxyribonucleotides only to 3’ end of growing chain

Is DNA polymerization endergonic or exergonic?

endergonic because it requires energy and is anabolic

monomers of DNA polymerase are

deoxyribonucleoside triphosphates (dNTPs)

a replication bubble forms when

DNA is being synthesized

Replication bubble in bacteria vs eukaryotic cells

Bacteria have one and form one replication bubble and eukaryotic have many on each chromosome

each replication bubble have 2 replication forks due to

synthesis being bidirectional and replication bubbles grow in 2 directions

Proteins responsible for opening and stabilizing double helix

DNA helicase, single strand dna binding proteins, topoisomerase

breaks down hydrogen bonds between two DNA strands to separate them and opens the double helix

DNA helicase

attach to separated strands to prevent them from closing and stabilizes the single stranded DNA

Single strand DNA binding proteins (SSBPs)

cuts and rejoins DNA to relieve twisting forces

Topoisomerase

DNA polymerase cannot

start synthesis from scratch on template strand

short strands of RNA and base paired to DNA template

primer

enzymes that make primers, a type of RNA polymerase, does not require free 3’ end to begin synthesis

primase

since DNA strands are antiparallel, the synthesis process

differs for each strand

Strand that is synthesized toward replication fork in the 5’ → 3’ direction

leading strand

extends the leading strand

DNA polymerase III

holds DNA polymerase in place during strand extension

sliding clamp

catalyzes the joining of okazaki fragments into a continuous strand, between 3’ to 5’, closes up backbone

DNA ligase

 Strand synthesized away from replication fork and occurs because DNA synthesis must proceed in 5’ -> 3’ direction

Lagging strand (discontinuous strand)

what is the Discontinuous replication hypothesis

Primase synthesizes new RNA primers on lagging strand as replication fork opens and DNA polymerase synthesizes short fragments of DNA along lagging strand, fragments are then linked into continuous strand

During Chase experiment, short radioactively labeled DNA fragments were found, short strands were attached to DNA primers, strands gradually became longer during chase

okazaki fragments

 Lagging strand is synthesized as

short discontinuous Okazaki fragments

Contains enzymes responsible for DNA synthesis around replication fork

replisome

Observation of individual proteins in replisome suggest

Replisome is dynamic, continuous strand may not be synthesized as continuously as once believed, rates of DNA synthesis may vary widely

Beadle and Tatum proposed discovering what genes do by

Damage a gene, then observe effect on phenotype

Nonfunctioning alleles are called

null or loss-of-function alleles

what is the one-gene, one-enzyme hypothesis

Each gene contains information to make an enzyme

Particular stretch of DNA (a gene) specifies

amino acid sequence of one protein

Found to carry information from DNA to site of protein synthesis

Messenger RNA (mRNA)

synthesizes RNA and uses DNA strand as template, Copies code by matching complementary nucleotides

enzyme RNA polymerase

The _______ of molecular biology summarizes the flow of information in cells

central dogma

DNA codes for proteins by

DNA → RNA → Proteins, DNA sequence codes for RNA sequence, RNA sequence codes for sequence of amino acids in protein

process of using DNA template to make complementary RNA making a copy of information

transcription

process of using information in mRNA to synthesize proteins and interprets nucleotide “language” to amino acids

translation

Determined by sequence of bases in DNA

genotype

Product of proteins it produces

phenotype

Alleles of the same gene differ in DNA sequence and proteins produced because

different alleles of the same gene frequently differ in their amino acid sequence

genes flow

DNA → RNA

flows from RNA back to DNA, synthesizes DNA from RNA template

Reverse transcriptase

specifies how a sequence of nucleotides codes for a sequence of amino acids

genetic flow

Three-base code is known as a

triplet code

Group of three bases that specifies particular amino acid

codon

Reading frame (sequence of codons) of gene could be destroyed by

adding or subtracting one or two bases but was not destroyed by adding or subtracting multiples of three bases.

RNAs are composed of

ribonucleotides

what is the start codon and what are the three stop codons

AUG is start and UGA, UAA, UAG are stop

the genetic code is

redundant, unambiguous, non overlapping, universal, conservative

Knowing the genetic code and the central dogma, biologists can

Predict the amino acid sequence by a particular DNA sequence and determine mRNA and DNA sequence that could code for a particular sequence of amino acids

mutations are

any permanent change in an organism’s DNA like modification in cell’s information archive,change in its genotype, new alleles

two types of mutations are

point mutations and chromosome level mutations

4 types of point mutations

missense mutations, silent mutations, frameshift mutations, nonsense mutations

mutation that changes an amino acid in protein

Missense mutations

mutations that do not change amino acid sequence due to redundancy in the code

silent mutations

mutations that shift reading frame, altering meaning of all subsequent codons

frameshift mutations