dna n inheritance

Question 1

what are histones?

Answer 1

proteins dna strands coil around

Question 2

what happens to DNA during cell division?

Answer 2

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

Question 3

what is a nucleotide?

Answer 3

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

Question 4

what are genes?

Answer 4

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

Question 5

what is a monomer?

Answer 5

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

Question 6

what are the 4 different bases?

Answer 6

guanine
cytosine
adenine
thymine

Question 7

what is the sugar phosphate backbone?

Answer 7

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

Question 8

what happens during DNA replication?

Answer 8

• 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

Question 9

what are proteins and examples?

Answer 9

long chains of amino acids

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

Question 10

what is mRNA?

Answer 10

• 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

Question 11

what is transcription?

Answer 11

• 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

Question 12

what is translation?

Answer 12

• 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

Question 13

what is the epigenome?

Answer 13

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

Question 14

what can influence gene expression?

Answer 14

• a change in the phenotype without changing the genotype

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

Question 15

what is acetylation?

Answer 15

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

Question 16

what is methylation?

Answer 16

when a methyl group (CH3) attaches to cytosine

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

Question 17

what are alleles?

Answer 17

alternative forms of the same gene

Question 18

incomplete dominance?

Answer 18

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

Question 19

co dominance?

Answer 19

a heterozygous individual expressed both simultaneously without any blending

Question 20

thalassemia (genetic disease)

Answer 20

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

Question 21

sickle-cell anaemia

Answer 21

• 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

Question 22

tay-sachs disease

Answer 22

• 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

Question 23

what is variation caused by?

Answer 23

• random assortment during meiosis
• crossing over during meiosis
• nondisjunction during meiosis
• random fertilisation

Question 24

what is random assortment?

Answer 24

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

Question 25

what is crossing over?

Answer 25

• 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)

Question 26

what is non disjunction?

Answer 26

• 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

Question 27

conditions resulting from nondisjunction?

Answer 27

• 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

Question 28

what is mitochondrial DNA (mtDNA)

Answer 28

• 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

Question 29

what is epigenetics?

Answer 29

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

Question 30

what is chromatin

Answer 30

a network of coiled DNA