Patterns of Inheritance 6.1.2 module 6

Question 1

what is continuous variation

Answer 1

value within a range/quantitative
eg) height, length of stalk

-genetic and environmental factors
-polygenic controlled by a number of genes
no limit on value, 2 extremes

can be shown through standard deviation curve

Question 2

what is discontinuous variation

Answer 2

distinct catagories
-qualitative
-eg) blood group, hair colour, wrinkle or smooth peas
-mongenic/controlled by one or two genes
limited number of phenotypes
no in between catagories

can be shown in bar chart

Question 3

what is an allele

Answer 3

a different form of the same gene

Question 4

what is a phenotype

Answer 4

characteristics displayed by an organism

Question 5

what is a genotype

Answer 5

the alleles an organism has eg) Bb BB bb

Question 6

what is a dominant allele

Answer 6

will always be expressed if present in genotype

Question 7

what is a recessive allele

Answer 7

expressed if two copies are present

Question 8

what are homozygous alleles

Answer 8

same alleles identical alleles for a gene can be dominant or recessive

Question 9

what are heterozygous alleles

Answer 9

different alleles present in the zygote

Question 10

what is the locus

Answer 10

position of a gene on each homologous chromosome

Question 11

what are homologous chromosomes

Answer 11

chromosomes w/ same structure features and patterns of genes

Question 12

what are Epigenetics

Answer 12

(means above genetics) the idea that both nature and nurture affect how an organism looks and acts
eg) rats mums and illnesses such as diabetes
both influenced by genes or lifestyle, look of leaf, obesity

Question 13

how can genes and environement effect leaf appearance

Answer 13

genes code for chlorophyll in normal genome

-environment has determined leaf appearance (physiology causes a change in phenotype)

Question 14

how can the environment effect the leaf appearance

Answer 14

Chlorosis- mineral deficiencies

• lack of Fe- cofactor for enzymes in chlorphyll production
• lack of Mg- (Mg is in chlorophyll) chlorophyll can’t be synthesised

also Virus infections which interfere w/ metabolism of chlorphyll production and leaves tissues turn yellow

Etiolation- lack of light- plants turn off chlorphyll production to conserve resources, plants grow abnormally long and spindly due to not enough light.

Question 15

arguments that obesity is caused by genes example

Answer 15

• ‘ob’ gene codes for secreted protein that may function in cell signalling pathway of adipose tissue so more fat deposits
• ‘LEP’ gene codes for hormone leptin which is produced by fat cells in proportion to their size eg) bigger cells=more leptin (hormone associated w/ satiety)

Question 16

arguments that obesity is caused by environment example

Answer 16

• inbalanced calories uptake and use
• availability of food
• diet choice

Question 17

what is a phenotype

Answer 17

characteristics displayed by an organism

Question 18

what is a genotype

Answer 18

the alleles an organism has eg. BB bb Bb

Question 19

what is a dominant allele

Answer 19

always expressed if present in genotype

Question 20

what is a recessive alleles

Answer 20

expressed if two copies are present

Question 21

what does homozygous mean

Answer 21

same alleles for gene eg BB or bb either recessive or dominant

Question 22

what does heteorozygous mean

Answer 22

different alleles are present in the zygote

Question 23

what is the locus

Answer 23

position of a gene on each homologous chromosome

Question 24

what are homologous chromosomes

Answer 24

chromosomes w/ same structural features and patterns of genes

Question 25

what is epigenetics

Answer 25

In biology, epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence.
idea of ‘nature vs nurture’
example being the rats mum and level of licking being down to nurture. But those that were licked less still had the methyl group attached which switched off the gene for licking. the methyl group is orgionally attached in all rat babies

Question 26

what is the enzyme used in transcription

what are the names of the strands of dna

Answer 26

rna polymerase - synthesising strand of mRNA
the coding/ sense strand 5’ to 3’
and the antisense/ template strand 3’ to 5’

Question 27

where does transcription occur

Answer 27

nucleus

Question 28

where does translation occur

Answer 28

ribosomes in cytoplasm

Question 29

which types of RNA are involved in translation

Answer 29

mRNA
tRNA
rRNA

Question 30

what does the tRNA have on it

Answer 30

anticodon complementary to codon which syntheisises an amino acid forming a polypeptide chain

look at 10/01/20 if dont understand

Question 31

order of a protein forming?

which enzymes involved

Answer 31

DNA replication- DNA polymerase involved forms DNA

Transcription- RNA polymerase involved forms mRNA

Translation- at the ribosome froms polypeptide/protein

Question 32

what is a degenerate code in terms of genetic codes

Answer 32

idea that more than one codon can code for amino acid! describes why silent mutations have no effect on phenotype

only 20 amino acids to code for but 64 cobinations of codons (4^3) so some code for same.

Question 33

what is meant by a non-overlapping code

Answer 33

Starts with AUG and ends with a stop codon and is read in 5’ to 3’ direction ensuring it is non-overlapping

adjacent codons don’t overlap and no base can take part in formation of more than one codon.

Question 34

what is meant by universal code

Answer 34

DNA is universal as all living organisms have genes made up of DNA

Question 35

what is a mutation

Answer 35

a change in the base sequence of DNA in cell division and copying which changes the arrangement of genes (structure of chromosome)

Question 36

how is albinism caused

Answer 36

enzyme involved in chemical pathway is effected so doesnt have correct active site and can’t catalyse the reaction pathway leading to the formation of melanin. This stops production of enzyme for this and cells cant produce melanin

Question 37

what type of nucleic acid holds together the bases i translation

Answer 37

mRNA

Question 38

what effect do stop codons have

Answer 38

ensure DNA is non overlapping
they dont code for an amino acid
aka nonsense or termination codons

Question 39

what name would be given to a mutation that changes UUU to UUC

Answer 39

substitution

Question 40

what are the 4 types of point mutations

Answer 40

substitution ATG&raquo_space; ACG
insertion ATG&raquo_space; ATCG G becomes part of next codon
deletion ATG&raquo_space; AG
inversion ATG&raquo_space; AGT

Question 41

which point mutations cause a frameshift and what does that mean

Answer 41

insertion and deletion
the addition or removal of a base alters the reading frame of a gene. It can change every codon after the mutation and can dramatically change the amino acid sequence

Question 42

if the base substitution is silent what does this mean

Answer 42

DNA sequence has changed but codon hasnt because the DNA code is degenerate

dont change phenotype and most mutations are this type&raquo_space;>neutral

Question 43

what is a missence base substitution mutation

Answer 43

DNA change single nucleotide change results in a codon that codes for a different amino acid (alters

this can have large effects such as sickle cell which is caused by base substitution

Question 44

what is a nonsense base substitution mutation

Answer 44

every amino acid coded for after that codon (stop codon) won’t be copied which can cause things like cystic fibrosis if chain stops early

Question 45

what is cystic fibrosis catagorised as

Answer 45

severe repiritory problems
inadequate pancreatic function caused by accumulation of sticky mucus

this is due to mutation in CFTR coding gene which means it the final protein can’t allow Cl- ions across cell membranes

Question 46

what kind of point mutation is cystic fibrosis usually caused by

Answer 46

deletion

nonsense

Question 47

how does a framshift effect the resulted protein/ polypeptide chain

Answer 47

completely inactive/ useless due to reading in translation

Question 48

examples of useful/beneficial mutations

Answer 48

> ability to digest lactose-spontaneous mutation but not in many mammals who develop intolerance after suckling
bacterial resistance by natural selection
rat poison resistance
camouflaging shell colours and banding on snails

Question 49

examples of detrimental mutation

Answer 49

> sickle cell anemia
albinism
cystic fibrosis
huntingtons

Question 50

how can sickle cell anemia be beneficial?

Answer 50

in areas where malaria is present, the parasite/plasmodium can only live in normal red blood cells so anyone heterozygous for sickle cell won’t suffer from malaria.

Question 51

how is sickle cell caused

Answer 51

base substitution mutation to mRNA base sequence in transcription and changes the polypeptide is haemoglobin as amino acid changes from Glu to Val

instead of globular protein a more fibrous stranded haemoglobin is formed. Hydrophobic VALine binds to other hydrophobic regions causes clumping and sickle cell shape

Question 52

what are the effects of sickle cell

Answer 52

> insoluble haemoglobin formed can’t carry oxygen as effectively so is tired constantly
can from clots in capillaries- blocks blood supply to vital organs
sickle cells destroyed more rapidly than normal red blood cells so low red blood cell count - anemic

Question 53

how can sexual reproduction lead to genetic variation within a species

Answer 53

meiosis and the random fusion of gametes at fertilisation

Question 54

what is monogenic inheritance

Answer 54

the inheritance of a single gene

Question 55

what is dihybrid inheritance

Answer 55

inheritance of two different characteristics caused by two genes which may be located on different pairs of homologous chromosomes
each of these genes can have 2 or more alleles

eg round and yellow peas ect