PSYB32H3 Chapter Notes -Sickle-Cell Disease, Mendelian Inheritance, Nitrogenous Base

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Published on 16 Oct 2013
School
UTSC
Department
Psychology
Course
PSYB32H3
genotype
o genes that a person inherits from their parents
o except twins, no two people have the same genotype
phenotype
o created by genotype and environment interacting
o can observe it in physical and behavioural characteristics
ovum
o female egg
o largest human cell
sperm
o smallest human cell
zygote
o cell formed from male and female cells
chromosomes
o thread-like structures in centre of cell
o helps to direct development
copies of the 23 pairs of chromosomes all get copied to every cell in the human body
except sex cells (they only get 23 single chromosomes)
o go through meiosis in which they cross over and make genetic variability
mitosis
o cell division where chromosomes are duplicated to daughter cells
o occurs in autosomes and sex chromosomes
autosomes
o non-sex chromosomes
o have matching pairs
Genes, DNA and Proteins
DNA
o stores genetic info
o made up of nucleotides
nucleotide
o compound that has a
nitrogen base
simple sugar
phosphate group
o AT, CG
genes
o part of DNA that codes for certain kinds of protiens
The Transmission of Traits: A Basic Model
Mendel studied pea plants, came up with 2 principles
principle of segregation
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o each inherited trait comes as a separate unit (e.g. flower colour), you do not get a
set of traits in a bundle
principle of independent assortment
o inheritance of traits occurs independently of each other e.g. flower colour does not
influence inheritance of stem height
the notion that if one parent is tall and the other is short then the child will be in between
is not accurate (since traits are inherited separately AA Aa aa)
alleles
o gene, we usually have 2, one from each parent
homozygous
o alleles for a trait are the same e.g. AA aa
heterozygous
o alleles for a trait that are different e.g. Aa
What happens when a trait is heterozygous? (3 possibilities)
combination of 2 dissimilar alleles can sometimes produce intermediate traits
both alleles express the trait at the same time, with equal force
o the two traits do not blend though
o e.g. blood type AB (A from one parent and B from the other)
only one of the alleles are expressed
Recessive Alleles
many harmful alleles are recessive
o this is very most societies prohibit incest
o 2 recessive alleles become expressed
Sex Chromosomes
23rd pair
female = XX
male = XY
X chromosome is longer and carries more genes
any recessive X-linked chromosomes in males will automatically be expressed (since
they only have one x)
hemophilia
o blood does not clot
Modifier Genes
genes that affect the expression of other genes
e.g occurrence of early cataract is determined by a dominant gene, but the fo0rmation is
influenced by modifier genes
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Document Summary

Genotype: genes that a person inherits from their parents, except twins, no two people have the same genotype. Phenotype: created by genotype and environment interacting, can observe it in physical and behavioural characteristics. Mitosis: cell division where chromosomes are duplicated to daughter cells, occurs in autosomes and sex chromosomes. Autosomes: non-sex chromosomes, have matching pairs. Dna: stores genetic info, made up of nucleotides. Genes: part of dna that codes for certain kinds of protiens. Mendel studied pea plants, came up with 2 principles. Principle of segregation: each inherited trait comes as a separate unit (e. g. flower colour), you do not get a set of traits in a bundle. Alleles: gene, we usually have 2, one from each parent. Homozygous: alleles for a trait are the same e. g. aa aa. Heterozygous: alleles for a trait that are different e. g. aa. What happens when a trait is heterozygous? (3 possibilities) combination of 2 dissimilar alleles can sometimes produce intermediate traits.

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