unit 4 topic 1 Flashcards
how is DNA stored and found in prokaryotic cells
the DNA found in prokaryotic cells is unbound, naked and circular. it is found free floating in the cytosol of the cell. this is the same for DNA stored in the mitochondria and chloroplast in eukaryotic cells
how is DNA found and stored in eukaryotic cells
DNA ladder is individual wrapoped twice around 8 histone (proteins) to form a nuclesome. packed nucleomse form chromatids which is tightly coiled into a chromsome
base paring rule in DNA
adenine (a) - thymine (t)
cytosine (c)- guanine (g)
base paring rule in RNA
adenine (a)- uracil (u)
cytosine (c)- guanine (g)
thymine (t) - adenine (a)
weak, base- specific hydrogen bonds between DNA strands
the role of hydrogen bonds in stabilizing the DNA double helix, however these bond are weak individually but collectively provide significant stability to the DNA structure there are also base-specific enduring the base pairing rule which is crucial for the accuracy for DNA replication and transcription
the process of DNA replication
the helicase enzyme binds to the DNA and breaks the hydrogen bonds between the 2 strand creating a replication fork. DNA polymerase binds to the primers on the loose DNA strand and starts synthesizing commentary strands to the parent strands (nucleotide pairs) as the new strand is synthesized in 5-3 direction. the leading strand is synthesized continuously towards the replication fork. the lagging strand is created discontinuous by moving away from the replication fork creating Okazaki fragments that are eventually joined together . DNA polymerase proofread their work
process of meiosis I and II and purpose
Prophase- homologs chromosome pair up to from chromosomal pair
Metaphase- homologous pair align the cells equator
Anaphase- homologous chromosome are speared and pulled to opposite sides of the cell
Telophase- nucleus membrane forms
purpose- to produce gametes, or sex cells
processes of crossing over
homologous chromosome become connected though synapsis. non-sister chromosome Brack away and recombined with there homologous partner effectively exchanging genetic material. with the non-sister chromatids remaining connected in X-structure with chiasmata. as a result of crossing over chromatid consist of a combination of DNA from each
process of independent assortment
the random pairing up of homologous pairs
during prophase I homologous chromosome line the equator, the paired chromosome can randomly arrange themselves in one of two orientations
paternal left/maternal right
maternal left/paternal right
the orientation of one homologous pair does not affect the orientation of any other homologous pair. independent assortment of chromosome creates 2 different gamete combination where n is the haploid number of chromosome
spermatogenesis
- located in testes
- the production of spermatozoa (sperm) in the seminiferous tubes of the testes
- begin at puberty
-process- spermatogonia undergo a period of mitotic cell growth, becoming primary spermatocytes (2n) which then undergo one meiotic division to form secondary spermatocytes (n), they then undertake a process of differentiation in order to become functional sperm cell know as spermatozoa (n)
oogenesis
-located in overise
-the production of female gametes (ova)
- occurs at two points- before birth (prophase I) and after birth (metaphase II)
- process
before birth - oogonia 92n) undergo a period of meiotic cell growth becoming primary oocytes (2n), the primary oocytes being meiosis I but stop in prophase II
puberty- primary oocyte (2) will complete meiotic division to form one secondary oocyte (n) and one polar body (n), which divides into 2 polar bodies. this happen during meiosis II halting at metaphase II just before ovulation
at fertilization- meiosis II resume when secondary oocyte is fertile, ovum (n) is produced and another polar body. ovum fuses with sperm nucleus to from zygote.
random fertilization of gametes
the fusion of two haploid gamete result in the formation of diploid zygote (can be divide by mitosis). random fertilization by egg and sperm will result in different zygotes. egg and sperm unit to form a zygote with the diploid number of chromosome’s
define genome
all the genetic material in the chromosome of an organism, including its genes and DNA sequence
gene
unit of heredity, a unique sequence of DNA that determines a characteristic of an organism
what is coding and no coding DNA
coding DNA- nucleotides sequence of DNA, which code for proteins
non-coding DNA- nucleotide sequence/region of DNA which do not code for proteins; however still may have another purpose such as tRNA, rRNA
transcription process
the process by which a DNA sequence (gene) is copied into a complementary mRNA sequence
initiation
1. RNA polymerase binds to the promoter after combining with other transcription factors
2.RNA polymerase then starts unwinding and separating the DNA strand by braking the H bond between nitrogenous bases
elongation
3.complementary RNA nucleotides are progressively joined together by RNA polymerase moving along the length of DNA template strand
- RNA polymerase binds the nucleotide together, synthesizing an mRNA strand in 5-3 direction
- DNA rewinds
translation process
the process which codon on the mRNA are translated into a sequence of amino acids, resulting in polypeptide chain
initiation
1. ribosome attaches to the 5’ end of the mRNA strand
2. ribosome reaches start codon of sequence (AUG)
2. tRNA molecule with anticodon- UAC bind to binding site at the ribosome and despots methionine, which is the first amino acid in the polypeptide chain
elongation
4. ribosome passes along mRNA strand and read condones from 5-3 direction
5. further tRNA molecule with anticodon complementary to the mRNA codons, binds to tRNA binding site of ribosome
6.tRNA deposit their amino acids, which attach to adjacent amino acid polypeptide through a peptide bond
7. process continues and the polypeptide chain growth
termination
8. attachment of amino acid continue until stop codon reaches
9. polypeptide chain released by ribosome into cytoplasm or rough Endoplasmic reticulum
purpose of gene expression
the expression of what genes are expressed where they are epxressed and when
gene regulation through protein synthesis
transcription factors- proteins that bind to specific DNA sequence near a gene to either promote or inhibit its transcription. they can enhance or block the ability to RNA polymerase to initiate transcription, through enhancers (decrease) silencers (increase) the rate of transcription
translations factors- RNA binding proteins that bind to mRNA molecules and influence their stability, localization or translation efficiency, microRNA- small RNA molecules that bind to mRNA and block its translation or lead to its degradation
gene regulation through the products of other genes
gene products- the proteins or RNA produce by other genes can affect the expression of a target gene
gene networks- gene do not operate in isolation; their expression can be influenced by the products of other genes in complex networks
gene regulation through environmental exposure
epigenetic modification- environmental factors can lead to changes in gene expression through modification to DNA or histone protein
twin studies- research on identical twin helps in understanding the role of environmental actors in gene regulation
example of transcription factors that regulate morphology
during embryonic development the differentiation of stem cells, lead more to tissue formation and morphological development in the organism
for example
hox gene- determined morphology (shape and form) or an organism
sex-determining region Y- example of cell differentiation found on the Y chromosome of males
DNA replication mutations
point mutation- change to one base in the DNA code
-the substation of a base ( ATG-ACG)
-the insertion of a base (ATC- ATCG)
-the deletion of a base (ATC-AG)
frame shift mutations- substitution or deletion of nucleotides in DNA sequence not divisible by 3
cell division mutations
the chromosome failing to separate correctly, resulting in gamest with an abnormal number of chromosome, can either occur via
-failure of homologues to separate during anaphase I (resulting in 4 affected daughter cells)
-failure of sister chromatids to separate during anaphase II (resulting in 2 affected Dougher cells)
