Topic 2 (2.11-2.16) Genes Flashcards
(34 cards)
what are DNA and RNA strands made up of
nucleotides- a polynucleotide chain formed by a condensation reaction. a phosphodiester bond forms between phosphate group and hydroxyl group (Prime 5 and prime 3) hydrogen bond forms between complimentary base pairs
what are the 4 complimentary base pairs of DNA & RNA
RNA= Uracil, Adenine, cytosine, Guanine
DNA =Thyamine, Adenine, Cytosine, Guanine
what are the complimentary base pairs ?
Thyamine/ Uracil + Adenine - Two hydrogen bonds between base pairs
Cytosine+ Guanine - Three hydrogen bonds between base pairs
what are purines and pyrimidines
purines are double ringed
(Adenine and Guanine)
Pyrimidines are single ringed
(thymine and cytosine)
purines and pyrimidines always join together
what are the differences between DNA and RNA
DNA - double stranded (double helix), Thymine instead of Uracil, deoxyribose sugar, larger molecule
RNA- single stranded ( one polynucleotide chain not coiled), Uracil instead of thiamine, Ribose sugar, smaller molecule
what molecules make up a nucleotide and what direction does a polynucleotide chain join
phosphate head, pentose sugar, base always form bond between phosphate head and prime 3 oh on pentose sugar
how is DNA formed
Enzyme DNA helices attaches to dna molecules and causes hydrogen bonds between complimentary basepairs to break
The two polynucleotide strands separate and new nucleotides line up agains complimentary base pairs of DNA strand forming hydrogen bonds between base pairs
the nucleotides that join are called active nucleotides which the 2 extra phosphate groups
DNA polymerase catalyses the formation of a phosphodiester bond and the 2 ppsphate groups are removed to provide energy for reaction
(condensation reaction)
other stand of DNA (lagging strand) moves in the opposite direction (strands are antiparallel)
shorter polynucleotide chains (okoxaki fragments) are joind together onto other strand using DNA ligase
one strand is continuously formed the other is made form shorted DNA strands
What type of replication is DNA and definition of the type
semiconservative- a dna molecule contains one original strand and one newly formed nucleotide strand
What is Amniocentesis
removing of 20cm amniotic fluid with needle and syringe (through the abdomen)
foetal cells taken from fluid via centrifugation
carries out about 15-17 weeks into pregnancy
1% risk of miscarriage
Results take a few weeks
what are two types of genetic screening prenatal tests
Amniocentesis
CVS - Chronic Villus Sampling
What is Chronic villus sampling
Small sample of embryonic tissue taken from placenta
removes using needle through he wall of abdomen or through vagina
carries out at 8-12 weeks
Quick results
Cant detect problems on X chromosomes as inactive
1-2% risk of miscarriage
what is pre implantation Genetic diagnosis/ example
couple can go for IVF during pre implantation genetic dignosis:
The female partner’s ovaries are stimulated to produce eggs.
The eggs are collected and fertilized with sperm in a lab.
A few cells are removed from the embryo.
The cells are tested for genetic conditions.
Embryos that are not affected by the condition are placed back into the womb.
how does ivf work: A needle is used to extract eggs from the ovaries
The eggs are kept in a culture medium
Male semen is mixed with the eggs
Fertilized eggs develop into embryos
The embryos are placed in a culture for several days
The embryos are transferred into the mother’s womb
pros and cons of prenatal screening
- could remove diversity
-lead to miscarriage
-could cause discrimination - could improve Childs quality of life
what is difference between transcription and translation
transcription- making of mRNA outside nucleus
translation- making of amino acids outside nucleus
what is the process of making mRNA (transcription) - transcription
RNA polymerase joins RNA molecules onto DND to form mMRN
what is the process of translation
mRNA leaves the nucleus and bins to the a rRNA and ribosomal subunit. That then signals tRNA to pair its anti code one onto the codon on mRNA; the start codon in AUG for methionine and anticodons can be degenerate and are non overlapping triplet codes. the Anti codon binds the the code using hydrogen bonds and and as a mother tRNA binds consecutively a peptide bond is formed between the amino acids and the tRNA molecule leaves. When the stop anticodon binds to the codon the amino acid sequence is completed and rRNA separates from ribosomal sub unit.
what is a codon
3 codes on mRNA base sequence of three nucleotides in DNA or RNA that codes for a specific amino acid
what is a non overlapping triplet code
Each set of three bases codes for 1 single amino acids - each base is only used, read once so there is no overlapping between codes when reading a sequence.
what is the meaning of degenerate
more than one codon can code for the same amino acid in the genetic code
what is an anticodon
it is the three base pairs on a tRNA which are complimentary to the a codon on mRNA molecule
mucus hydration regulation in a normal human
mucus hydration regulation in cystic fibrosis human
what is the named experiment for semiconservative replication
Meselson and Stahl experiment
what is the method go the MS experiment ?
DNA was cultured on heavy nitrogen (n 15) for several generations. That DNA was the cultured on nitrogen 14 (light nitrogen) for one generation.
after centrifugation there was a a band with nitrogen 15 and nitrogen 15 showing that there was a new strand and and original strand ( conservative replication). Generation 2 has a higher band as the lower band has original nitrogen 15 and new nitrogen 14, new higher band has original nitrogen 14 new nitrogen 14 after replication. highest nitrogen 14 band becomes thicker because new strands of DNA have only nitrogen 14 more DNA made from only light nitrogen.
name types of mutations and mutation definition ?
Mutations are permanent changes in the DNA of organisms.
types include:
inversion - swapping order or bases
deletion - removal of base
insertion - adding of bases
duplication - 2 of same bases
substitution - base substituted for another
