dna n inheritance Flashcards Preview

human biology > dna n inheritance > Flashcards

Flashcards in dna n inheritance Deck (30)
Loading flashcards...
1
Q

what are histones?

A

proteins dna strands coil around

2
Q

what happens to DNA during cell division?

A

dna remains intact, when the coiled chromatins become even more tightly coiled (chromosomes)
structure of DNA is twisted into a double helix

3
Q

what is a nucleotide?

A

each phosphate group and sugar molecule with a nitrogenous base is a nucleotide.

4
Q

what are genes?

A

sections of the DNA. molecule that contain the genetic code (stored information + codes for activities)

5
Q

what is a monomer?

A

a single molecule that can join together to form a larger molecule
made up of nucleotides joined together

6
Q

what are the 4 different bases?

A

guanine
cytosine
adenine
thymine

7
Q

what is the sugar phosphate backbone?

A

-DNA is a polymer of mononucleotides- join together between the phosphate of one nucleotide and the sugar (deoxyribose) group of the adjoining nucleotide.

8
Q

what happens during DNA replication?

A
  • 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
9
Q

what are proteins and examples?

A

long chains of amino acids

  • haemoglobin
  • actin + myosin
  • albumin
  • amylase
  • collagen
10
Q

what is mRNA?

A
  • 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
11
Q

what is transcription?

A
  • 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
12
Q

what is translation?

A
  • 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
13
Q

what is the epigenome?

A

-a set of chemical compounds and proteins that attach to DNA that act like switches and markers that influence gene expression

14
Q

what can influence gene expression?

A
  • a change in the phenotype without changing the genotype

- life style changes alter how our genes vegans without actually changing genetic makeup eg smoking

15
Q

what is acetylation?

A

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

16
Q

what is methylation?

A

when a methyl group (CH3) attaches to cytosine

  • CpG
  • prevents RNA polymerase from reading the gene
  • inhibits gene expression— turns the gene off
17
Q

what are alleles?

A

alternative forms of the same gene

18
Q

incomplete dominance?

A

a blend of the two heterozygous alleles giving rise to a third phenotype

19
Q

co dominance?

A

a heterozygous individual expressed both simultaneously without any blending

20
Q

thalassemia (genetic disease)

A
  • recessive
  • abnormal haemoglobin production = anaemia
  • frequent blood transfusions due to excess build up of iron
  • frequent in mediterranean countries
21
Q

sickle-cell anaemia

A
  • 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
22
Q

tay-sachs disease

A
  • 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
23
Q

what is variation caused by?

A
  • random assortment during meiosis
  • crossing over during meiosis
  • nondisjunction during meiosis
  • random fertilisation
24
Q

what is random assortment?

A
  • during the first meiosis division, homologous pairs are separated at random
  • chromosomes move to opposite poles
25
Q

what is crossing over?

A
  • 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)
26
Q

what is non disjunction?

A
  • 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
27
Q

conditions resulting from nondisjunction?

A
  • 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
28
Q

what is mitochondrial DNA (mtDNA)

A
  • 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
29
Q

what is epigenetics?

A

a set of chemical compounds and proteins that attach to DNA and act like switches and markers that influence gene expression

30
Q

what is chromatin

A

a network of coiled DNA