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GP 1, 2 and 3

Chapter 3 Human Dev

Psych 30

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1. How does conception

normally occur? This is an egg cell

(ovum) surrounded

by sperm

fertilization (alsocalled conception)

takes place when

one sperm unites

with an ovum toform single new cell.

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1. How does conception

normally occur? The new cell is

called a

Zygote

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Development of the zygote

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Ovulation

Ovulation is the

process in the

menstrual cycle by

which a matureovarian follicle

ruptures and

discharges an ovum

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2. What causes multiple births?

There are two basic

types of twins:

monozygotic (also

known as "identical")and dizygotic (also

known as fraternal").

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Dizygotic twins

Dizygotic twins are

no more alike than

any other2 siblings

would be

Both can be the same

sex or they can be

opposite sexes.

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Monozygotic twins

Monozygotic twinshave identicalhereditary makeup

howeverenvironmentalfactors will certainlycause somedifferences to occur.

Also some identicaltwins are mirrorimages

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3. How does heredity operate in

determining sex andtransmitting normal and

abnormal traits?

Each cell in the

human body

contains up to

100,000 genes

which are located

on chromosomes.

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DNA

Genes are

composed ofDNA.

Every cell in the

human body (exceptthe gametes or sex

cells) has 46

chromosomes.

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23 to 46

The sex cells

undergo a division

called meiosis

which gives them23. When 2 gametes

fuse during

reproduction the

zygote ends up with46 chromosomes

again.

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karyotype

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Sex Chromosomes

Autosomes are the 22

sets of chromosomes

which are not related to

reproduction . The sexchromosomes are the

chromosomes which

determines whether a

baby will be a boy or a

girl.

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Sex Determination 50/50

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Dominant and Recessive Alleles

Tongue curling is a

dominant gene each

person has a set of

alleles (genes) for each

trait (one gene from

the mother and one

from the father) The

dominant allele is

always expressed. Ifyou can curl your

tongue that is your

phenotype .

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Phenotypes and Genotypes

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Phenotype/Genotype

Your phenotype is what people can observe

about you (tongue rolling, eye colour etc.)

YourGenotype is what alleles (genes) you

have. People cannot necessarily see whattype of genes you have. For example if you

have brown eyes you may have 2 dominant

alleles or you may have 1 dominant and one

recessive (blue eyed) allele all people canobserve is the phenotype (brown eyes)

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Chromosomal Abnormalities

Also called Downs

Syndrome

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Trisonomy 21

Characterized by

Mental retardation

Downward sloping skin fold on eyes

a single instead of a double crease acrossone or both palms

shorter limbs

poor muscle tone Protruding tongue.

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Hemophilia

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Sex Linked Traits