1. Heredity

2. Mendel and Heredity Heredity: is the passing of traits
to offspring from its parent.
Traits- characteristics that are
inherited such as eye color, leaf
shape, tail length
Genetics- study of inheritance
patterns and differences (variation)
in organisms
Gregory Mendel- father of genetics
for discovering traits (heredity units)
Recognized that genes determine traits by experimenting with pea plants. For example, he crossed or mated 2 pea plants that were purple. The offspring produced were purple and white. White was a hidden or masked trait!

3. Key Vocabulary
Gene- a piece of DNA that provides instructions to make proteins in a cell
EX: gene for flower color of pea plant– white or purple
Allele- any alternative form of a gene
EX: White and purple color alleles
Homozygous (purebred)- two of the same alleles
EX: 2 alleles for white color (tt)
EX: 2 alleles for purple color (TT)
Heterozygous( Hybrid)- two different alleles
EX: 1 allele for purple and 1 for white (Tt)

5. Genotype- genetic makeup (specific genes) for an individual EX: BB, tt
Phenotype- physical characteristics or traits for an individual EX: brown eyes or short peas

6. EX: Rr, RR= round is dominant
Dominant- allele that is expressed when 2 different alleles are present
The dominant allele IS EXPRESSED or seen in the phenotype (physical traits).
EX: Rr, RR= round is dominant
Recessive- allele that is only expressed (shown) when 2 copies of allele are present
The recessive allele is MASKED
by the dominant allele.
Recessive allele (form of gene)
is NOT EXPRESSED or seen in
phenotype (physical traits).
EX: rr= wrinkled is
recessive

7. Punnett Squares
Mother’s Genes (egg)
Punnett Square- grid system for predicting all possible genotypes from a cross of 2 mates
Can determine probability of offspring have a specific genotype and phenotype
Father’s Genes (sperm)

8. Bb bb B b Key B= brown eye allele b= blue eye allele
Dominant trait _______
Recessive trait_______ b
Genotype Percentages
Homozygous/Pure Recessive_____
Homozygous/Pure Dominant_____
Heterozygous/Hybrid ____ b
Phenotype Percentages
Brown Eyes_______
Blue Eyes________
Brown Bb bb
Blue
50% 0%
50%
50%
50%

9. TT Tt Key T= Tall allele t= short allele T t Dominant trait ______
Recessive trait__ _ T
Genotype Percentages
Homozygous/Pure Recessive _____
Homozygous/Pure Dominant______
Heterozygous/Hybrid______ T
Phenotype Percentages
Tall ________
Short____
Tall TT Tt
Short 0%
50%
50%
100% 0%

10. ff Key F= purple flower allele f= white flower allele f f
Dominant trait _________
Recessive trait_________ f
Genotype Percentages
Homozygous/ Pure Recessive_____
Homozygous/Pure Dominant______
Heterozygous/Hybrid______ f
Phenotype Percentages
Purple Flower _____
White Flower_____
purple ff
white
100% 0% 0% 0%
100%

11. Environmental Factors Affect Gene Expression
Environmental conditions can cause a gene to be expressed/activated or not expressed/deactivated (turned on).
Environmental factors such as hormones, temperature and chemicals can influence gene expression.
Example: Himalayan Rabbits has fur that changes color according to outside temperature. If the outside temperature is cold, the fur grows in black. If the temperature is warm, the fur grows in white. The outside temperature causes the activation or inactivation of genes for fur color.
Example: Identical twins raised in different environments show differences that are caused by the environment affecting gene expression.

12. Let’s Practice
1. Identical twins were separated at birth and raised by different families. The best explanation for any differences between the twins in height, weight, and IQ scores is that the genes regulating these traits were
independently assorted
codominant
linked
environmentally influenced

13. 2. If the pattern of inheritance for a trait is complete dominance, then an organism heterozygous for the trait would normally express
the recessive trait, only
the dominant trait, only
a blend of the recessive and dominate traits
a phenotype unlike that of either parent

14. 3. When a certain pure strain of fruit fly is cultured at a temperature of 16°C, all of the fruit flies will develop straight wings. The offspring of these flies will develop curly wings if they are developed at 25°C. This pattern of development indicates that
acquired characteristics can be passed from generation to generation
curly-winged flies will have straight-winged offspring regardless of the environment
the environment can affect the expression of certain genes
straight-winged flies will have curly-winged offspring regardless of the environment

15. 4. A woman has a gene that causes a visual disorder
4. A woman has a gene that causes a visual disorder.  To prevent the disorder from appearing in future generations, the defective gene would have to be repaired in the mother’s
nervous system
reproductive cells
eye
uterus

16. 5. The diagram represents the change in a sprouting onion bulb when sunlight is present and when sunlight is no longer available. Which statement best explains this change?
Plants need oxygen to survive.
Environmental conditions do not alter characteristics.
Plants produce hormones.
The environment can influence the expression of certain genetic traits.

17. 6. Which sequence of terms represents a decrease from the greatest number of structures to the least number of structures present in a cell?
nucleus → gene → chromosome
gene → nucleus → chromosome
gene → chromosome → nucleus
chromosome → gene → nucleus

18. 7. Which statement best explains the fact that some identical twins appear different from one another?
Their DNA is essentially the same and the environment plays little or no role in the expression of their genes.
Their DNA is very different and the environment plays a significant role in the expression of their genes.
Their DNA is very different and the environment plays little or no role in the expression of their genes.
Their DNA is essentially the same and the environment plays a significant role in the expression of their genes.

19. 8. The transfer of genes from parents to their offspring is known as
differentiation
heredity
immunity
evolution

20. 9. Which statement best explains the change shown in the diagram below?
Gene expression in an organism can be modified by interactions with the environment.
Certain rabbits produce mutations that affect genes in specific areas of the body.
Sorting and recombination of genes can be influenced by very cold temperatures.
Molecular arrangement in existing proteins can be altered by environmental factors.

21. 10. A human liver cell and a human skin cell in the same person have the same genetic sequences. However, these cells are different because the liver cell
has more dominant traits than the skin cell
can reproduce but the skin cell cannot
carries out respiration but the skin cell does not
uses different genes than the skin cell

22. 11. Several structures are labeled in the diagram of a puppy shown below. Every cell in each of these structures contains
equal amounts of ATP
identical genetic information
proteins that are all identical
organelles for the synthesis of glucose

23. 12. A boy inherits genes for tallness, but his growth is limited as a result of poor nutrition. This is an example of
an inherited disorder
environmental influence on gene expression
expression of a hidden trait
a characteristic controlled by more than one pair of genes

24. 13. The diagram below represents a structure found in most cells
13. The diagram below represents a structure found in most cells. The section labeled A in the diagram is most likely a
protein composed of folded chains of base subunits
biological catalyst
part of a gene for a particular trait
chromosome undergoing a mutation

25. 14. As male children get older, some begin to closely resemble their fathers and have no resemblance to their mothers. Which statement best explains this observation?
Several sperm fertilized the egg, so the fertilized egg contained more genes from their father.
More genes are inherited from the sperm cell of their father than from the egg cell of their mother, so most traits will be like those of their father.
More genes from their father are expressed in traits that can be seen, and more genes from their mother are expressed in traits that cannot be seen, such as blood type or enzyme function.
Genes from their father are stronger than genes from their mother, so the genes from their mother are not expressed.

26. 15. Which statement best describes a human chromosome?
It is made of amino acid subunits that form genes.
It contains genes that may code for the production of enzymes.
It is normally passed to the next generation through a placenta.
It varies in function from one generation to the next.

27. 16. The diagram below represents the banding pattern for human chromosome 11, with some of the bands labeled. The bands represent
proteins
genes
starches
enzymes

28. 17.In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). If 50% of a large litter of squirrels are gray, the parental cross that produced this litter was most likely
GG x Gg
GG x GG
Gg x gg
gg x gg

29. 18. The diagram below represents levels of organization within a cell of a multicellular organism. Which statement is correct regarding
the structure represented by X?
(1) Structure X is composed of many different
amino acids that determine the type of cell it
will become in the organism.
(2) Structure X has the same base sequence in
all the body cells of the organism.
(3) Structure X is a folded chain
arrangement of carbohydrate found
in all the body cells of the organism.
(4) Structure X contains 20 different
kinds of subunits that are present in
all the cells of the organism.

30. 19. Which represents the genotype of a homozygous condition?Bb BC bb bc

31. 20. When many hybrid tall pea plants are cross-pollinated, the offspring produced will probably be
100% homozygous tall
100% heterozygous tall
50% homozygous tall
50% heterozygous tall

32. 21. The outward appearance (gene expression) of a particular trait in an organism is referred to as
a genotype
a phenotype
an allele
a chromosome

33. References McDougal Littell Biology Living Environment Textbook
The Living Environment Prentice Hall Brief Review for the New York Regents Exam