1.6 Match the sentence halves
1Genetics is the study of genes, the branch of
2 A gene is the basic unit of hereditary a segment
3 Some alleles can be
4 You will look more like your mother if
5 A cell also a code that
6 When a cell divides, the DNA code is
7 Every cell in your body
8 The color of your hair and your height depend on
9 Protein consists of
10 The codes for making proteins are carried from the nucleus
A is stored in its hereditary material.
B chains of hundreds or thousands of amino acids.
C of DNA that codes a particular trait
D contains DNA.
E biology that deals with the study of heredity
F dominant and others can be recessive
G to the ribosomes by the nucleic acid called RNA.
H copied and passed to the new cells.
I the kinds of proteins your cells make.
J you get a dominant gene from her
1.7 Say whether these statements are true or false
1 The traits that are inherited from parents can be brown or blue eyes; black, brown, blond, or red hair.
2 Genetic principle which accounts for the transmission of traits from parent to offspring is the gene.
3 Genetics is the branch of anatomy that deals with the study of heredity.
4 A gene is the basic unit of hereditary, a segment of DNA that decodes a particular trait.
5 Genes control the form and the function of an organism's body.
6 Alleles are different forms of a trait that a gene may have.
7 Alleles can be of two types.
8 A cell also uses a code which is called RNA.
9 DNA contains information for an organism's growth and function and is stored in cells that don’t have a nucleus.
10 The DNA code is copied and passed to the new cells during the process of cell division.
11 Every cell in your body or in any other organism contains DNA.
12 Most of your characteristics depend on the proteins your cells produce.
13 Proteins have different functions. They build cells and tissues or work as enzymes.
14 Protein contains chains of hundreds or thousands of amino acids.
15 The order of amino acids in a protein is determined by DNA.
16 If you change the order of the amino acids you will get a different protein.
17 Proteins are found in the nucleus, but genes are made on ribosomes in the cytoplasm.
18 The codes for making proteins are carried from the ribosomes to the nucleus by RNA.
1.8 Ask questions to the text
1.9 Summarize the text
II. Genetic variation
2.1 Read the text and answer the following questions
a. Why is genetic variation important for individuals?
b. How does variation happen in asexual reproduction?
c. How does variation happen in sexual reproduction?
Sources of variation
Genetic variation is important because when conditions change some individuals will be more likely to have variations that will allow them to survive. Those who reproduce pass their genes to the next generation. Variation helps species survive, and it's the reason why species change over time.
In asexual reproduction, variation comes mainly from mutation. Mutation is a natural process that introduces permanent changes in a DNA sequence. In sexual reproduction, variation comes from both mutation and recombination. Mutation creates the different versions (or alleles) of the same gene. Parental alleles are then shuffled—or recombined—during meiosis. Because of recombination, sexual reproduction produces more variation than asexual does.
Sex chromosomes
What chromosomes determine the sex of an individual?
What chromosomes do females have?
What chromosomes do males have?
Do other living things have sex chromosomes?
What chromosomes do birds and reptiles have?
Does the sex of living things depend only on the chromosomes?
In most mammals, the X and Y sex chromosomes determine whether an individual is male or female. Females have two X chromosomes, and therefore two copies of every gene. Males, however, have one X and one Y chromosome. For genes that appear only on the X chromosome or only on the Y (some do appear on both), males inherit just one copy.
Other living things have sex chromosomes too. Birds and reptiles have Z and W sex chromosomes. Unlike with X and Y, males have two Z chromosomes, and females have one Z and one W. Some insects and a few mammals have only an X chromosome. Females have two copies and males have one. However, sex is not always determined by chromosomes. With alligators, crocodiles, and most turtles, it's egg incubation temperature. And some fish can change gender in response to cues from the environment. Sex determination happens in many different ways.
Unit VII