Biology Final Exam Review Flashcards
what is DNA?
nucleic acid
DNA consists of individual units call…
nucleotides
what are the 3 units of a nucleotide?
molecule of sugar, phosphate group, and a nitrogenous containing molecule base
DNA bases are connected with what?
hydrogen bonds
what us a full set of DNA present in an individual called?
genome
in prokaryotic cells including bacteria, DNA is…
contained within circular pieces of DNA
in eukaryotes including humans, information in the DNA is…
laid out in long linear strands of DNA in the nucleus
eukaryotic DNA exists as many smaller, more manageable pieces called
chromosomes
how many chromosomes do we have?
46
the location or position of a gene on a chromosome is called what?
locus
what is a gene?
a sequence of base pairs in a DNA molecule that carry the information necessary for producing a functional product, usually a polypeptide or RNA molecule
each gene is the instruction set for producing one particular molecule usually what?
protein
what are alleles?
alternative versions of a gene that code for the same feature
what is a trait?
any single characteristic or feature of an organism
example of allele and genes and traits
The color of a daisy’s petals is a trait. the instructions for producing this trait are many different alleles; one allele may specify the trait of red pedals, another may specify white petals, another yellow petals.
what are the 2 types of nucleic acid?
DNA and RNA
what plays a central role at producing of proteins?
DNA and RNA
in what type of organism do we find the most “junk DNA?
bacteria and viruses tend to have very little non-coding DNA
what is hydrogen bonding?
chemical attraction in which an electronegative atom (oxygen,nitrogen) of one molecule is attracted to a hydrogen atom of another molecule
the nucleic acids of DNA and RNA are macromolecules that…
store information
how does RNA differ from DNA?
- the sugar phosphate bone contains an extra atom of oxygen
- RNA is single stranded
- A, U, G, C
what are introns?
where about 25% of the non-coding regions occur within genes
where do 75% of non-coding regions occur?
between genes
what is a genotype?
genes that an organism carries for a particular trait
what is phenotype?
the physical appearance
How does a gene affect the phenotype?
the process occurs in two main steps: transcription and translation
what happens in transcription?
a copy of gene’s base sequence is made
what happens in translation?
the copy is used to direct the production of a polypeptide which then in response to a variety of factors, including cellular environment, folds into a functional protein
in transcription, the gene’s sequence is copied from DNA to a molecule called what?
mRNA
in translation, the gene’s sequence is now encoded in mRNA, which directs the production of a what?
protein
where does transcription occur for eukaryotes?
in the nucleus
where does transcription occur for prokaryotes?
cytoplasm
what happens after transcription?
the mRNA then moves out of the nucleus into the cytoplasm, where translation allows the message encoded in the mRNA to be used to build proteins
what happens in transcription?
1) the enzyme RNA polymerase recognizes a promoter site. RNA polymerase binds to the DNA molecule at the promoter site and unwinds it just a bit, so that only one strand of the DNA can be read.
2) RNA polymerase builds a copy called “transcript”. This copy is called mRNA. Throughout, DNA is unwound ahead of the RNA polymerase so that a single strand of DNA can be read
3) when the RNA polymerase encounters a sequence of bases on the DNA at the end of the gene, it stops creating the transcript and detaches from the DNA molecule. after termination, the mRNA molecule is released as a free-floating, single stranded copy of DNA
4) a cap and tail are added for protection and to promote recognition and non-coding sections are removed
what is a promoter site?
a sequence in a gene that indicates the start of the gene and in effect tells the RNA polymerase to start
why is mRNA called mRNA?
because once this copy of the gene is created, it can move elsewhere in the cell and its message can be translated into a protein
when does translation process begin?
once the mRNA molecule has moved out of the cell’s nucleus and into the cytoplasm
what is necessary for translation to occur?
large numbers of free amino acids & ribosomal subunits
what are ribosomal subunits?
components of ribosomes, the protein-production factories where amino acids are linked together in the proper order to produce the protein
what is tRNA?
molecules that interpret the mRNA code
how many possible codons are there?
64
what happens in translation?
1) the start sequence AUG is recognized by tRNA molecule and 2 ribosomal subunits
2) ribosome moves along mRNA
the codon to start in translation is always what?
AUG
what is gene expression?
only thing that matters when carrying a gene; the production of the protein that the gene’s sequence codes for
what is gene regulation?
whether a gene is turned on - producing its protein product - or turned off
cytoplasm contains specialized structures called what?
organelles
a human has how many genes?
30,000 - 35,000
the average gene size is what?
3,000 bases
genes make up less than how much of DNA?
5%
where do introns occur?
within genes
how do genes work?
transcription - copy of a gene’s base sequence is made
translation - copy is used to direct the production of a protein
what happens after completion of translation?
mRNA strand may remain in the cytoplasm
where are mRNA strands eventually broken down after translation?
cytoplasm
what are the termination stops?
UAA, UGA, UAG
where are telomeres located?
at the tip of every chromosome
what is the function of telomeres?
keeps track of how many times the cell has divided & acts like a protective cap at the end of the DNA
for what is telomere rebuilding essential?
single-celled organisms and reproductive cells
why can telomere rebuilding be a big problem?
the cells are unable to stop dividing. such cells commonly go by another name: cancer
where do prokaryotic cells carry their genetic information?
in a single, circular chromosome
what is the chromosome strand of a prokaryotic cell attached to?
cell membrane
what methods do prokaryotes use to reproduce?
binary fission - “division in two”
what is the first step to cell division?
replication –> creates exact duplicate of each chromosome
what happens in prokaryotic cell division?
1) chromosomes attach to the inside of the plasma membrane at different spots
2) parent cell pinches it until it divides into 2 cells aka daughter cells
3) binary fission considered asexual reproduction because the daughter cells inherit DNA from a single parent cell and are genetically identical to the parent
what are the 2 types of cells?
somatic and reproductive cells
eukaryotic chromosomes are composed of DNA and what?
chromatin
somatic cells go through __ and reproductive cells go through ___
mitosis; meiosis
the eukaryotic cell cycle
G1: growth phase. A cell grows and carries out its normal cellular functions
S: cell replicates its DNA in preparation for next division
G2: growth and preparation for division
M: mitotic phase; cell divides DNA and all organelles then splits into 2 daughter cells
apoptosis = ?
cell death
WBCs engulf vesicles through the process called ___
phagocytosis
replication begins where?
origin of replication where the DNA unwinds and separates into 2 strands like a zipper
what is the enzyme at the origin of DNA replication?
DNA helicase
what is mitosis responsible for?
growth and replacement of old and damaged cells
where does the most rapid cell division take place?
bone marrow and in the cells lining like tissues and organs
what happens during S-phsae of interphase?
sister chromatids are formed
each pair of sister chromatids are held at the center by what?
centromere
how many homologous chromosomes do humans have?
46
steps of mitosis
1) interphase: chromosomes replicate in preparation for mitosis
2) prophase: pair up!
3) metaphase: chromosomes meet in the middle. long microtubules attach to each chromatid at the kinetochore
4) anaphase: chromosomes get pulled apart
5) telophase: now there are 2 chromosomes
what is cytokinesis?
driving of the cytoplasm
what is meiosis?
process that enables organisms, prior to fertilization, to make special reproductive cells called gametes
how many chromosomes do gametes have?
half as many as the rest of the cells in the body
what does meiosis do to each individuals genome?
reduce it by half
how many chromosomes can gametes have?
23 chromosomes
what is a diploid?
refers to cells that have 2 copies of each chromosome
what is a haploid?
refers to cells that have one copy of each chromosome
what are the 2 important outcomes of meiosis?
1) it reduces the amount of genetic material in gametes
2) it produces gametes that all differ from each other with respect to the combinations of alleles they carry
what does asexual reproduction result in?
identical offspring because of type of replication
where does meiosis take place?
gonads
where does mitosis take place?
all over the body`
what happens in prophase 1?
where crossing over takes place
interphase occurs first,meiosis 1 (separate homologous pairs), meiosis 2 (separate sister chromatids)
.
what happens in anaphase 1?
where random assortment occurs
where do the sources of genetic variation come from?
2 gametes
what is the sexual reproduction advantage?
introduces greater variance
