ISCI Exam 2

What is a gene?

a section of DNA that contains instructions for building a protein

what is a gentotype?

your genes or DNA

what is a phenotype?

your physical appearance

what can contribute to physical appearance?

environment

where are genes found in eukaryotes?

nucleus

does DNA look like in eukaryotes?

spaghetti noodles

DNA + Histones = ?

chromatin

what is DNA wrapped around proteins called?

histones

What are histones?

proteins

most cells have how many of each chromosome?

2

What is a diploid?

2 sets of each chromosome

What is a haploid?

one set of chromosomes

What are homologous chromosomes?

chromosomes that are the same

what kind of cells are haploid cells?

sex cells

How many chromosomes do humans have?

46 (23 pairs)

What are autosomes?

pairs 1-22 of chromosomes

What are sex chromosomes?

pair 23 of chromosomes that determines a persons gender

what does XX chromosomes mean?

female

what does XY chromosomes mean?

male

Who discovered DNA?

Watson and Crick

how did Watson and Crick discover DNA?

by using an x-ray that was taken by Rosalind Franklin

what did Watson and Crick use the x-ray for?

to figure out the structure of DNA

what kind of model was DNA replication follow?

semiconservative

What does semiconservative DNA replication mean?

That each daughter DNA strand contains one strand from the parent and one that is newly synthesized

what does the parent strand serve was in DNA replication?

template strand

where does DNA replication start?

origin of replication

What does topoisomerase do?

relax the strands

what does helicase do?

separates the strands

when is the replication fork created?

when helicase separates the strands

what happens at the replication fork?

proteins bind to the exposed strands

What does primase do?

synthesizes a short RNA sequence/RNA primer

What does DNA polymerase do?

adds new DNA nucleotides to the 3' end of the primer

what is the leading strand?

template strand where nucleotides are added from 5' to 3'

What is the lagging strand?

at replication fork, primase adds RNA primer

DNA strands go in what direction?

5' to 3'

what is the central dogma?

DNA -> RNA -> Protein

what is transcription?

the gene's sequence is copies from DNA to a middleman called mRNA

what is translation?

the gene's sequence is now encoded in mRNA, which directs the production of a protein

what are the steps of transcription?

Recognize and bind, transcribe, terminate, cap and process

what happens during the recognize and bind stage of transcription?

RNA polymerase recognizes a promoter site and it binds one strand of the DNA and starts reading the gene

what happens during the transcribe stage of transcription?

the RNA polymerase builds a single stranded RNA copy of the gene called mRNA transcript

what happens during the terminate stage of transcription?

when the RNA polymerase encounters a code signaling the end of the gene, it stops transcription and releases the mRNA transcript

what happens during the cap and process stage of transcription?

in eukaryotes mRNAs receive extra processing before they can be translated into a protein, a cap and tail are added for protection and to promote recognition and NON CODING SECTIONS ARE REMOVED

what are the steps of RNA processing?

gene > mRNA transcript > processed mRNA

What happens in translation?

converts info carried by mRNA into functional proteins

what must be present in the cytoplasm for translation to occur?

free amino acids, ribosomal subunits, tRNA

what is tRNA?

molecules to read mRNA and translate that message from a sequence of bases into a protein

What is the start codon?

AUG

what are the stop codons?

UAA, UAG, UGA

what happens in the first step of translation?

recognize the start codon and ribosomal subunits

what are the ribosomal subunits?

E > P > A

what happens in the E site?

tRNA exits the ribosome

what happens in the P site?

grow proteins and the very first tRNA comes in

What happens at the A site?

all other tRNA molecules enter here

what is a genetic mutation?

when the sequence of nucleotides in an organism's DNA is changed

what can a genetic mutation lead to?

changes in structure and function of proteins produced

What are most mutations?

neutral

where do most mutations occur?

in non-coding regions

what kind of cells can mutations occur in?

gamete producing cells and non sex cells

what are gamete producing cells?

sex cells

what do mutations in sex cells not have?

adverse health effects on the carrier

What is a point mutation?

change of one base pair

what are the examples of a point mutation?

one bp is substituted for another, a bp is inserted or deleted

are insertions/deletions or substitutions more dangerous?

insertions/deletions

what are chromosomal aberrations?

entire sections of a chromosome are altered

what are examples of chromosomal aberrations?

deletion of an entire section of DNA, relocation of an entire section of DNA, duplication of genes

What is a spontaneous mutation?

mutations arise by accident as long stands of DNA are duplicating themselves

what are radiation-induced mutations?

ionizing radiation has enough energy to disrupt atomic structure by removing bound electrons

what are chemical induced mutations?

chemicals can also react with the atoms in DNA molecules and induce mutations

what's an example of radiation-induced mutations?

UV rays

what's an example of something that can cause a chemical induced mutation?

cigarettes

Who is the father of genetics?

Mendel

how did Mendel learn about heredity?

by conducting experiments

What are Mendel's Laws?

segregation, independent assortment, dominance

what are the two types of traits?

dominant and recessive

What is a dominant trait?

A trait that masks the effect of the recessive trait

What is a recessive trait?

a genetic factor that is blocked by the presence of a dominant factor

What does homozygous mean?

inherits the same 2 alleles for a gene

What does heterozygous mean?

inherits a different allele from each parent

What is Mendel's Law of Segregation?

Alleles pairs separate during gamete formation, and reunite randomly at fertilization

What is Medel's Law of Independent Assortment?

alleles at different loci separate independently

what is Mendel's law of dominance?

dominant and recessive alleles are defined by their action when they are in the heterozygous state

What is incomplete dominance?

phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes

What is codominance?

the heterozygote displays characteristics of both homozygotes

example of incomplete dominance

red x white = pink

example of codominance

speckled white and purple flowers

when does multiple allelism occur?

when there are three or more alleles for a gene within a population

what is a perfect example of multiple allelism and codominance?

blood type

what is a polygenic trait?

something that is controlled by multiple genes

what is the additive effect?

alleles of multiple genes all contribute to the ultimate phenotype

what is pleiotrophy?

when an individual gene influences multiple unrelated genes

what is an example of pleiotrophy?

sickle cell anemia

how many genes do humans have in our genome?

21,000

how many unique chromosomes do humans have?

23

why does it seem that some genes are linked?

because they fail to separate during crossing over in meiosis

what is multiple allelism?

when a single gene has more than two alleles

What do antigens do?

turn on a body's defense system

What type of antibodies does type A blood produce?

b

what type of antibodies does type B blood produce?

a

what type of antibodies does type AB blood produce?

none