dna n inheritance Flashcards
what are histones?
proteins dna strands coil around
what happens to DNA during cell division?
dna remains intact, when the coiled chromatins become even more tightly coiled (chromosomes)
structure of DNA is twisted into a double helix
what is a nucleotide?
each phosphate group and sugar molecule with a nitrogenous base is a nucleotide.
what are genes?
sections of the DNA. molecule that contain the genetic code (stored information + codes for activities)
what is a monomer?
a single molecule that can join together to form a larger molecule
made up of nucleotides joined together
what are the 4 different bases?
guanine
cytosine
adenine
thymine
what is the sugar phosphate backbone?
-DNA is a polymer of mononucleotides- join together between the phosphate of one nucleotide and the sugar (deoxyribose) group of the adjoining nucleotide.
what happens during DNA replication?
- this occurs before cell division
- happens during interphase of mitosis and meiosis
- an enzyme (helicase) causes the 2 strands of DNA to split
- free roaming nucleotides in the nucleus are attracted to their complimentary base pairs
- the string sugar phosphate backbone is rejoined by DNA polymerase
- each new DNA molecules consists of 1 parent strand and 1 new one
- an enzyme rewinds the double helix
what are proteins and examples?
long chains of amino acids
- haemoglobin
- actin + myosin
- albumin
- amylase
- collagen
what is mRNA?
- messenger ribonucleic acid (RNA)
- DNA that contains genes are too big to leave the nucleus pores, so a copy of the gene is made instead in the form of mRNA
- Uracil is used instead of thymine
what is transcription?
- the process in which a copy of DNA is made (mRNA)
- mRNA is single strand
- Helicase unzips DNA exposing the nitrogen base code
- RNA polymerase works along the template strand and adds new nucleotides; U to A, A to T, C to G and G to C
- mRNA leaves nucleus and carries genetic message to the ribosomes which are the protein-synthesising structures of the cell
what is translation?
- process in which genetic code carried by mRNA directs ribosomes to connected amino acids to eachother to produce proteins
- proteins assembled by ribosomes which line the ER or float around cytosol
- individual molecules of transfer RNA have a sequence of 3 nucleotides (anticodon) thag bind to the complimentary triplet (codon) in mRNA
- each anticodon bind to a specific amino acid
what is the epigenome?
-a set of chemical compounds and proteins that attach to DNA that act like switches and markers that influence gene expression
what can influence gene expression?
- a change in the phenotype without changing the genotype
- life style changes alter how our genes vegans without actually changing genetic makeup eg smoking
what is acetylation?
when a ACETYL group (COCH3) attaches to a histone, causing histone to spread, making it easier for DNA to be read by the RNA polymerase, ENHANCES gene expression
what is methylation?
when a methyl group (CH3) attaches to cytosine
- CpG
- prevents RNA polymerase from reading the gene
- inhibits gene expression— turns the gene off
what are alleles?
alternative forms of the same gene
incomplete dominance?
a blend of the two heterozygous alleles giving rise to a third phenotype
co dominance?
a heterozygous individual expressed both simultaneously without any blending
thalassemia (genetic disease)
- recessive
- abnormal haemoglobin production = anaemia
- frequent blood transfusions due to excess build up of iron
- frequent in mediterranean countries
sickle-cell anaemia
- recessive, autosomal disease
- common in areas of a malaria endemic
- crescent shaped blood cells, reduces amount of oxygen can be carried
- causes RBC to stick together and block up blood vessels
- usually fatal
tay-sachs disease
- autosomal recessive disorder
- inability to metabolise lipids due to a missing enzyme
- accumulation of fatty substances in the nervous system and brain
- affects sight, hearing, movement and mental development. death in early childhood
- jewish heritage and french canadian/cajun heritage
what is variation caused by?
- random assortment during meiosis
- crossing over during meiosis
- nondisjunction during meiosis
- random fertilisation
what is random assortment?
- during the first meiosis division, homologous pairs are separated at random
- chromosomes move to opposite poles
what is crossing over?
- alleles in chromosomes are inherited as a group
- which ever gamete inherits that chromosome during meiosis will receive all alleles in that particular chromosome
- during interphase 1 chromosomes are duplicated and become visible, pair of chromatids joined at centromere- chromatids get tangled with one another
- when 2 chromatids cross is called chiasma
- chromatids may break and reattach to other chromatids on chromosomes = new combo of alleles (recombination)
what is non disjunction?
- when chromosomes in the first meiotic division and chromatids in 2nd meiotic division fail to seperate
- results in one daughter cell receiving an extra chromosome and another daughter cell lacking a chromosome
- either 22 or 24 chromies
conditions resulting from nondisjunction?
- trisomy: when an individual inherits an extra copy of a chromie (down syndrome- trisomy 21)
- monosomy: when an individual is missing a chromosome > results in malformation or miscarriage
- Partial trisomy or monosomy: part of chromosome is missing out there is an extra copy of the chromosome
what is mitochondrial DNA (mtDNA)
- small amount of DNA located in mitochondria
- circular molecules not bound to proteins
- rare diseases caused by mutations in mtDNA
- ovum have hundreds of mitochondria whilst sperm only has a 100
- sperm mitochondria is destroyed during fertilisation
- therefore mtDNA is inherited from our mothers
what is epigenetics?
a set of chemical compounds and proteins that attach to DNA and act like switches and markers that influence gene expression
what is chromatin
a network of coiled DNA
