Summary

Summary - PYC 1512

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Course
PYC 1513

Institution
PYC 1513

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Uploaded on May 16, 2024
Number of pages 13
Written in 2023/2024
Type Summary

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Unit 1

Genes & Chromosomes: Inheritance occurs through genes on chromosomes.
Gregor Mendel: Demonstrated gene inheritance patterns.
Chromosome Pairs: Each parent contributes one chromosome to each pair.
DNA Structure: Double helix structure composed of nucleotides with adenine,
guanine, cytosine, and thymine.
Gene Types:
Dominant: Strong effect in both homozygous and heterozygous conditions.
Recessive: Shows effect only in homozygous condition.
RNA: Single-strand chemical synthesized from DNA, involved in protein synthesis.
RNA Bases: Adenine, guanine, cytosine, and uracil (replaces thymine).

Genetic Variants: Homozygous (same genes on both chromosomes) and heterozygous
(unmatched gene pairs).

Genetics focuses on genes, units of heredity passed down through generations.

Genes come in pairs aligned on chromosomes, with each parent contributing one to
each pair.
Chromosomes, composed of DNA, carry genetic information and replicate to
maintain the genetic code.
DNA consists of nucleotides with four bases (adenine, guanine, cytosine, thymine),
forming a double helix.
RNA, synthesized from DNA, aids in protein synthesis.
Genes can be homozygous (same genes on both chromosomes) or heterozygous
(unmatched genes).
Genes can be dominant (strong effect in homozygous or heterozygous condition),
recessive (effect shown only in homozygous condition), or intermediate.

Sex-linked and Sex-limited Genes

Sex-linked genes are located on the sex chromosomes (X and Y in mammals), with X-
linked genes being more common due to the Y chromosome's small size.
In mammals, females have two X chromosomes (XX), while males have one X and
one Y chromosome (XY).
During reproduction, females contribute an X chromosome, while males contribute
either an X or a Y chromosome.
Offspring with XX genotype develop as females, while those with XY genotype
develop as males.
Sex-linked genes are primarily found on the X chromosome.

, Sex-limited genes are present in both sexes but are only active in one sex.
These genes, like those responsible for beard growth in men and breast size in
women, typically show their effects during puberty.

Gene changes

Genes typically remain stable, but they can undergo changes, primarily through
mutation.
Mutation is a permanent alteration in the genetic material of an organism, which can
involve changes in chromosome number or arrangement (chromosomal mutation)
or alterations in DNA composition affecting one or a few bases (point mutation).
Mutations can occur spontaneously or due to exposure to external factors like X-
rays or chemicals.
Somatic mutations, occurring in body cells, are not inheritable, while germ-line
mutations, occurring in reproductive cells, can be passed on to offspring.
Another type of mutation includes duplication (part of a chromosome appearing
twice) or deletion (a chromosome not appearing at all), with microduplication and
microdeletion affecting small portions of chromosomes.
Duplications and deletions can contribute to various psychological, neurological,
and psychiatric disorders.

Epigenetics

Epigenetics involves changes in gene expression without altering the DNA sequence.
Genes can be switched on or off based on experiences, leading to changes in gene
function.
For instance, consistent love and nurturing can activate "attachment" genes in
children, while lack of stimulation can switch them off.
Adaptations to environmental conditions, like the ability to live at high altitudes in
Nepal, can also result from epigenetic changes.
Negative experiences, such as childhood trauma or drug addiction, can lead to
epigenetic changes in gene functioning.
These epigenetic changes can be passed down for at least a generation or two,
influencing the traits and behaviors of offspring.

Heredity and environment

Observable differences between people may stem from differences in heredity or
the environment.

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