Transcript Understanding Genetics

Understanding
Genetics
Unit 2
Bell Ringer
October 19 th , 2011
Of your family members
who do you feel you act
like, look like, etc.?
Heredity
 The biological process by which
certain traits are transmitted
from parents to their children
 Genetics

The study of how traits are
passed from parents to child
through heredity
It all starts with….

Chromosomes

Long,
threadlike
structures in
the nucleus
or central
portion, of
each human
cell

CELL: Basic unit of all living matter (Adult = over 10 trillion cells)
CYTOPLASM: Substance of a cell outside of the nucleus
NUCLEUS: Central point of cell /
contains genetic coding for maintaining
life systems and issuing commands for
growth & reproduction
CHROMOSOMES:
46 in each Nucleus (23 pairs)
GENES: bands on chromosomes
(thousands of genes)
DNA on genes (billions of DNA)
GENES

On each chromosome
there are hundreds or
thousands of genes

Hereditary
unit that
determines a
particular
trait
T Genes carry
 2. _______
inherited traits that are
passed on from generations
to generations. Hundreds of
thousands of genes, which
make up the traits of
human beings, are carried
on every chromosome.
Dominant and Recessive traits

What happens when one parent carries the
trait for blue eyes and one carries the trait
for brown eyes?

Dominant


Stronger trait
Recessive

Weaker trait
 Heterozygous (hybrid):

having dissimilar pairs of alleles for any hereditary characteristic

Rr
 Homozygous (purebred)

: having identical pairs of alleles for any given pair of heredity
characteristics

RR, rr

T
4. _______ Dominant genes are
stronger genes and recessive genes
are weaker.


T
5. _______ In the formation of a new
individual where the genes are both
recessive and dominant, the
dominant will overpower.

DOMINANT
Brown hair
Other Color hair
Brown eyes
Straight hair line
Free Earlobes
Roll Tongue
Second finger shorter then the 4th
Hitchhiker’s thumb
RECESSIVE
Blonde hair
Red hair
Blue Eyes
Widows peak
Attached earlobes
Can’t roll tongue
Interlock hands and right thumb on top
No hitchhiker’s thumb
Dominant vs.
Recessive
a.
widow’s peak
a.
b.
Unattached earlobe
a.
c.
Attached earlobe
Short fingers
a.
d.
Continuous hairline
Long fingers
Freckles
a.
Lack of freckles
Punnett Square
T
6. _______ It is probable that a
dominant brown-eyed mother and a
recessive blue-eyed father will have a
brown-eyed child.
Wife B Wife b
Husban
d B
Husban
d b
BB
bB
Determine the chances of passing on a genetic
trait in the following situation:

The wife is blue-eyed and carries genes for
blue eyes on both of the chromosome pairs.
The husband is brown eyed and carries a gene
for brown eyes on one of the pairs and a gene
for blue eyes on he other one of the pairs.
Complete the following grid to determine the
chances for each of their children to be born
with blue or brown eyes.
B = dominant brown gene b = recessive blue
gene
Bb

There is a _____________________ in four
chance that the child will have brown eyes and
carry a gene for blue eyes.

There is a _____________________ in four
chance that the child will have blue eyes and
carry genes for only blue eyes.
bb

T
7. _______ It is probable that a child
can have recessive light colored hair
even though both of his parents have
dominant dark colored hair.
Red Hair and blue –green eyes
Recessive (weaker) genes will
not produce the
characteristic unless
transmitted by both
parents.
Gender Determination

Females:XX

Males: XY

Gender is
determined by
the male
Multiple Births


Fraternal Twins:

The ovary releases two separate eggs and each is
fertilized by a different sperm cell.

Can be boy and girl

Do not look exactly alike
Identical twins

A single egg is fertilized and then splits into two

Both boys or girls

Look very much alike
MULTIPLE BIRTHS
F

12. _______ Fraternal non-identical
multiple births that come from two
different eggs will look
.
identical
like
siblings.
F Identical
13. _______
multiple births that
come from one
fertilized egg
can
will be the
different
samesexes.
sex.

F
14. _______
Double
Conjoined
jointed
twins
twins
are when the ovum splits
apart but the separation
is not complete.
CONJOINED TWINS
Conjoined twins result when
a fertilized ovum begins to
split into two parts, but does
not fully complete the
process. The babies are joined
at whatever location does
not complete the splitting
process.
Genetic Disorders

Medical conditions caused by errors in
genes or chromosomes

Down syndrome

Cystic fibrosis

Muscular dystrophy

Sickle cell disease

Tay- sachs disease

PKU
Activity
Genetic Gamble
Genetic Counseling

Genetic counselors help provide
families with the information they
need to understand genetic
disorders.
Activity: Gene O Gram