Bio test 2 pt 1: genes and chromosomes and mutations

genome

all the genetic material of an organism that is transmitted from patents to offspring

T

T/F: the sequence of a genome is the sequence of all nucleotides along the DNA molecule in a cell

gene

the basic unit of inheritance

• the region of DNA in a chromosome that codes for a particular protein

locus

the physical site or location of a gene on a chromosome

same

a given gene is always found in the __ position on both of the chromosomes in a homologous pair

allele 

one of the two or more alternative forms of a gene that are found at the same locus

does not

the number of genes in a genome and the size of a genome ___ correlate closely with the complexity of an organism

histones

proteins that help compact DNA into the microscopic space of the nucleus

chromatin

the material that makes up eukaryotic chromosomes, consists of a DNA molecule complex with histone proteins

• occupies a smaller volume than all of DNA alone

• uncondensed

unreplicated chromosome

consists of a single, long DNA double helix wrapped around proteins (which are too small to distinguish at this scale)

replicated chromosome

consists of 2 copies of the same DNA double helix

sister chromatids

2 identical chromatid copies in a replicated chromosome

condensed replicated chromosome

consists of DNA condensed around its associated proteins, resulting in a compact chromosome that is 10,000 times shorter that its original length

centromere

holds replicated chromosomes together/region where sister chromatids are most closely joined to each other

chromatid

one double stranded DNA copy of a replicated chromosome with its associated proteins

asexual reproduction

2 identitcal daughter cells are produced

sexual reproduction

offspring receive genetic material from 2 parentsm

meiosis 

leads to the production of sperm and eggs

gametes

specialized cells that contain each parent’s genomes

ex: sperm and eggs

mitosis

leads to the production of non-gametes (somatic cells)

cytokinesis

what phase is both mitosis and meiosis followed by?

cytokinesis

the division of cytoplasm into two distinct cells

interphase

Gap 1, synthesis, and gap 2`

G1

growing, synthesizing proteins, cellular contents excluding the chromosomes are duplicated

S

synthesis/ DNA replication 

G2

cell duplicates genome and makes final adjustments before cell division

• double checks duplicated chromosomes for error

G0

when the cell “takes a break”

• not actively dividing or prepping to divide

ploidy

the number of sets of chromosomes in a cell

Haploid cells

contain 1 copy of each chromosome

• 1n

Diploid cells

contain 2 copies of each chromosome

• 2n

polyploid cell

contain more than 2 copies of each chromosome

• usually plants

fertilixation

when two gametes fuse and become 2n

autosomes

what are numbers 1-22 called in a karyotype of humans?

sex chromosome

what is chromosome 23 called in human karyotypes?

anomalies, sex 

from karyotypes you can see…

homologous chromosomes

chromosomes that have the same genes in the same position and are the same size and shape

different, not identical

In homologous chromosomes, the alleles are often ___ between the homologs and are therefore ___ chromosomes

nonsister chromatids

chromatids on different members of a homologous chromosomes pair

identical

in replication, the new DNA molecules are ____

single chromosome

as long as the 2 sister chromatids resulting from replication are joined at their centromeres, this is considered _____

amount DNA, number of chromosomes

replication doubles the ___, but not the ____

origins

DNA mutations are the ___ of genetic variation

mutations

• permanent change

• errors in DNA replication 

• caused by stress or damage to the cell (UV radiation and chemical exposure

• can create new alleles

• cane be beneficial, neutral, or deleterious 

sequence of DNA

the ___ allows it to specify exact copies of itself through a process called replication

• must be exact

semiconservative model of repliaction

every new DNA strand will have one parental strand and one new daughter strand

5’ to 3’

DNA polymerase replicates DNA by synthesizing a new strand in the ____ direction

3’ OH

incoming nucleotides in DNA replication are added to a free ___

transcription

just like ___ DNA polymerase reads 3’ to 5’ and synthesizes 5’ to 3’

3’ to 5’

DNA polymerase reads the DNA strand in the ___ direction

leading strand

made in the straight forward way with the daughter strand growing in the direction of the replication fork 

lagging strand

DNA is synthesized in small chunks that are eventually linked together

• discontinuous

• needs to be reinitiated

okazaki fragment

small new chunk of DNA

leading strand

1. DNA is locally unwound by an enzyme called helicase

2. RNA primase adds a primer so that there is a free 3’ OH to join onto

3. 5’ to 3’ synthesis

lagging strand

1. primer added

2. first fragment synthesized

3. second fragment synthesized

4. DNA polymerase 1 replaces RNA primer with DNA nucleotides

5. gaps closed by DNA ligase

helicase

catalyzes the breaking of hydrogen bonds between base pairs to open the double helix

DNA primase 

catalyzes the synthase of the RNA primer and the RNA primer on an okazaki fragment

DNA polymerase III

extends leading strand and okazaki fragments

DNA polymerase I

removes RNA primer and replaces it with DNA

DNA ligase

catalyzes the joining of okazaki fragments into a continuous strand

phosphordiester bonds

what kind of bonds does DNA ligase catalyze

mismatch repair

a process when proof reading by DNA polymerase has been completed and there is still a mismatch base pair, the cell corrects mistake

exonuclease activity 

when DNA polymerase detects a mismatch pair and corrects it

• does it while it works

beneficial mutation

increase the fitness of an organism

fitness

ability to survive and reproduce

neutral mutation

have no effect on fitness

deleterious mutation

most individuals are well adapted to their currnt habitat so it lowers fitess

environment 

whether mutation is harmful or beneficial is not a property of the mutation alone, it depends on the ___

silent mutation

change in teh nucleotide sequence that does not change the amino acid specified codon

• no change, neutral

missense mutation

change in nucleotide sequence that changes the amino acid specified by a chodon

• changes in primary structure of protein, beneficial or deleterious

nonsense mutation 

change in nucleotide sequence that results in an early stop codon 

• leads to mRNA breakdown or shortened polypeptide, deleterious 

frameshift mutation

addition or deletion of a nucleotide

• reading frame is shifted, altering the meaning of all subsequent codons, almost always deleterious

loss of stop

change of a stop codon to a sense codon

• additional amino acids are added tot eh end of the protein, may be deleterious depending on how many extra amino acids are added