Sttrcuture And Function Id Dna Flashcards
Genetics
science about heredity and variations of living organisms.
variation
Variation is divergence of species in their biological properties.
Heredity(inheritance)
The ability of organisms to transit their biological traits to their progenies
Who did genetics originate from
Gregor Mendel
Griffiths experiment
-Mice got injected with live smooth cells of pneumococcus and did
-Mice got injected with heat killed smooth cells and mice survived
-mice got injected with live rough cells of pneumococcus and survived
-mice got injected with mixed heat killed smooth cells and live rough cells and mice died.Live cells could be isolated from the dead mouse
Conclusion:transformation of rough cells into smooth cells killed mice
What is the transforming principle
In 1943, O. Avery with colleagues showed that some morphological and pathogenic properties could be transferred from smooth pneumococcal strain to the rough by DNA extracted from the virulent smooth strain.
Chargaff’s rules
Chargaff’s rules (1950):
- Amount of purine is equal to the amount of pyramiding in dna
A% = T%
2.proportion of AT bases could be different from GC bases(variation is species dependant)
DNA components
Each nucleotide includes at c carbon,phosphate and a nitrogenous base
Complementary base pairing
-pyrimidien base=cytosine ans thymine
-purine =adenine and guanine
Replication of dna
-Semi conservative replication
-every dna strand serves as a template for the synthesis of the complementary strand
How are protein made from dna
DNA
Replication
Transcription
Translation
Protein
Types of rna involved in protein synthesis
Messenger
Transfer
Ribosomal
Genetic processes that contribute to variation
Mutations
Recombination
Transpositions
Location of dna in the cell
In cytoplasm of prokaryotes
In nucleus, mitochondria and plastids of eukaryotes
DNA coiling in the chromosome
-DNA surrounds histones (proteins) and forms nucleosomes.
-They are arranged into solenoids.
-Solenoids make chromatin loops (units of chromatin in the chromatids of chromosome).
A chromatid is one of two copies of a replicated chromosome.
During cell division, the copies are joined (and later segregated into daughter cells) at the region called the centromere
Satellite dna
is highly repetitive DNA that is different in base composition from the majority of DNA in eukaryotic species. The majority of satellite sequences have increased AT content (65–80%)*. This difference allows to separate satellite DNA as one or more distinct bands during centrifugation with cesium chloride.
Some proportion of satellite DNA is a part of centromere structures (responsible for separation of chromosomes to daughter cells during cell division)
How was satellite dna discovered
-genomic dna is fragmented and centrifuged
-when reaching equilibrium dna bands settle based on density
Details of gene structure
Enhancer is bound by activator proteins (transcription factors) to start transcription.
The TATA box is a non-coding DNA sequence (known as a cis-regulatory element). It indicates a start of reading and decoding of a genetic sequence. Transcription factors bind TATA box and recruit RNA polymerase, which synthesizes RNA from DNA.
Details of gene structure
AATAAA is a conserved sequence of polyadenylation signal site
Uni-parental inheritance:
Inheritance of traits from only one parent
Bi parental inheritance
Inheritance of traits from both parents
From organelle is variation controlled by
Variegation Trait is controlled by genes in cytoplasm
Telomeres
=chromosomal ends(dna+ proteins)
-specialised DNA-protein complexes at the ends of chromosomes.
Telomeres are needed for protecting integrity of chromosomes and, therefore, for genome integrity
Genome
Complete set of genetic in formation of an organism
Plastome
Genome of plastids
Mitopchondriome
Genome of mitochondria
Epigenome
Description of all chemical modifications of dna ans histone proteins that regulate gene expression within the genome
Genotype
Combination of alleles for a particular gene or locus
Types of alterations to genetic material
-small changes in dna sequence
-rearrangemnts of genes and chromosomes
-deletions and insertions of dna sequences
-increasing or decreasing Chromosomal sets
Types of impact of gene alteration
Neutral
Beneficial
Harmful
Mutations
are random, inheritable (usually small) alterations in the sequences of a genome. Mutations can change the phenotype. Some of them (which are neutral) do not change the phenotype
Mutagens
are physical or chemical factors that increase the rate of mutations (in this case they are called induced mutations).
Mutagens can modify DNA in different ways, but those changes are considered as mutations when they are inherited.
Type of point mutations
Point mutations could be of two general categories:
- base–pair substitutions (one nucleotide is substituted with another);
- base–pair insertions or deletions (the nucleotides are inserted [added] or deleted
Effect :
Base–pair substitutions may lead to silent, missense, or nonsense mutations.
Insertions and deletions are mutations that have much more dramatic, disastrous effects on resulted proteins than substitutions do.
This is because mRNA is read as triplets of nucleotides (one triplet for one amino acid) during translation (protein synthesis); and the insertion or deletion of nucleotides alter the reading frame of grouped triplets, leading to a shift in genetic message (a frameshift mutation).
Types of base pair substitition
ubstitution is called a silent mutation if it has no effect on the encoded protein (because of the redundancy of the genetic code: a few different triplets could encode the same amino acid).
A substitution is a missense mutation if the altered codon causes encoding for a different amino acid (makes not right sense).
A substitution is a nonsense mutation if a codon for an amino acid is converted into a stop codon (it terminates translation, and a protein could be truncated
What type of mutation is sickle cell disease
a point missense mutation.
The allele causing sickle–cell disease differs from the wild–type (normal) allele by a single DNA base pair (A instead T leads to the synthesis of the aminoacid valine instead glutamine in the molecule of haemoglobin)
Achondroplasia
Mutation which causes abnormality in cartilage formation that delays bone growth,active mutant receptor leads to shortened bones
50% chance of passing the gene to children
Hutchinson-Gilford progeria syndrome:
autosomal dominant syndrome
GGC mutates to GGT
Translocation associated with chronic myelogenous leukemia (CML)
CML patients possess an abnormally short chromosome 22 (called Philadelphia chromosome), and an abnormally long chromosome 9 that are resulted from the reciprocal translocation. They have leukaemia, due to unregulated growth of predominantly leukocytes in the bone marrow (disorder of stem cell differentiation).
Down syndrome
most common type of viable human aneuploid
Characteristic facial features for a child with Down syndrome.
The other signs are short stature, heart defects, susceptibility to respiratory infection, and mental retardation. The patients are prone to leukemia and Alzheimer′s disease.
.
They have a shorter life span (some live to middle age). Most are sterile and sexually underdeveloped.
Basic biological functions of dna
In general:
Functions in heredity (based on exact copying of DNA during replication).
Functions in variations (based on recombination of DNA and different types of genome alterations – mainly as errors in replication of DNA and segregation of chromosomes). DNA variations are implicated in evolution of species. In many cases, however, they lead to serious diseases
Coding functions
Non coding functions