OCR Biology Patterns of Inheritance 6.1.2 Revision Summary - By A* Student
19 views 1 purchase
Course
Patterns of Inheritance 6.1.2 (H420)
Institution
OCR
A revision summary of OCR A level Biology Patterns of Inheritance 6.1.2
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Gene A sequence of base nucleotides that determine a characteristic. Monohybrid inheritance – the inheritance of a single
Allele
A variation of a gene gene
Allele freq
Total no. of times a allele is in a gene pool at a given time Genetic Cross
LocusThe position of a gene on a chromosome 1. Parental phenotype Red Red
Genotype
Genetic makeup of an organism 2. Parental genotype Rr Rr
Phenotype
Visible characterises of an organism 3. Gametes (in circle) R or r R or r
Homozygous
Pure breeding: 2 identical alleles at gene locus on homologous chromo 4. Punnet Square R r
heterozygous
Have 2 different alleles at gene locus on homologous chromosome (genotype) R RR Rr
Monogenic
Determined by a single gene r Rr rr
Dominant
Gene is always expressed if present 5. F1 generation phenotype 3 red: 1
recessive
Only expressed if gene is homozygous white
F1 generation
Produced from crossing parents - Carrier = heterozygous individual who has
F2 generation
Produced from crossing F1 recessive gene that is not expressed but can still
Linkage
When 2 or more genes loci are on the same chromosome. pass it on.
- 4 phenotypes, no ratio Test Cross – used to identify unknown genotype
Sex Linkage Gene is present on one sex chromosomes - Cross unknown genotype with Homozygous
Codominance 2 alleles are equally dominant & expressed in phenotype. 1:2:1 recessive
Autosome Any chromosome that isn’t a sex chromosome - If F1 gen express recessive gene, unknown must be
Monohybrid Inheritance of one gene, 3:1 heterozygous.
Dihybrid Inheritance of two non-interacting genes, 9:3:3:1 Codominance - two different alleles for the same gene
Epistasis The interaction 2+ genes at different loci are equally dominant and both expressed in genotype.
Recessive = 9:3:4, Dominant = 12:3:1/ 13:3, complementary 9:7 - Allele is subscripted to the gene.
Chromosome mutation – during meiosis F1 cross.
- Deletion – portion is lost 1. Parental phenotype Pink Pink
- Inversion – section inverts, now to far away from regulator gene to be expressed Flower Flower
- Translocation – piece of one chromosome becomes detached & attaches to 2. Parental genotype C C
R w
CRCW
another 3. Gametes (in circle) CR or CW CR or CW
- Duplication – piece is duplicated & now over expressed 4. Punnet Square C R
CW
- Non-disjunction – chromosomes fail to separate. CR CRCR CRCW
Aneuploidy – chromones not exact multiple of haploid C W
C C
R W
CWCW
Polyploidy – diploid is fertilised by a haploid = triploid. 5. F2 generation phenotype 1 Red: 2 Pink: 1 White
Plant mutations from environmental factors. Blood type has multiple alleles for the gene (I) each
- Chlorotic plants – have genotype to make chlorophyll but not enough Mg 2+ in soil codominant.
- Etiolation – not enough light means plant grows long & spindly. - IA = antigen A, IB = antigen B, IO = no antigen
(recessive)
Sex chromosomes
Human female = XX = homogametic – only one gamete Sex linkage – inheritance of trait is limited by alleles located on sex chromosome
Human male = XY = heterogametic – different gametes Haemophilia – sex-linked genetic disorder caused by recessive allele only on X
which determine sex
X chromosome much larger than Y, in males:
Only the homologous region pairs up
In non-homologous region: X chromosome has alleles not
present in Y.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller hyaldridge. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.11. You're not tied to anything after your purchase.
