Heredity

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!

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)

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

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

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)

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%

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%

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%

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.

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

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

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

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

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.

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

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.

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

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.

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

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

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

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

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.

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.

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

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

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.

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

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

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

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