key terms.

Question 1

What is adenine?

Answer 1

The base that combines with thymine to form a base pair. Adenine is one of the four letters that make up the genetic code in humans and other living things.

Question 2

What is an allele?

Answer 2

A version of a gene. An organism gets two alleles of each gene – one from its mother and one from its father.

Question 3

What is an amino acid?

Answer 3

A small molecule that joins with others to form proteins. Amino acids are the building blocks of proteins, which are the building blocks of cells.

Question 4

What is anaphase?

Answer 4

A stage of cell division in which the chromosomes separate. Anaphase is when the chromosomes separate and are pulled away from each other to opposite sides of the cell.

Question 5

What is a base?

Answer 5

Part of a DNA molecule that comes in four types: A, C, G and T. Bases join together in pairs to form the ‘rungs’ of the DNA molecule.

Question 6

What is a base pair?

Answer 6

Two bases joined together. Base pairs form in only two combinations: A-T or G-C. These are the letters that make up the genetic code.

Question 7

What is the cell cycle?

Answer 7

The repeated process of cell growth and division. During most of the cell cycle, a cell grows and performs its function. This ends when the cell divides by mitosis.

Question 8

What is cell division?

Answer 8

The splitting of a cell to form new cells. Cell division allows organisms to grow, repair damage and reproduce. There are two types: mitosis and meiosis.

Question 9

What is a chromosome?

Answer 9

A DNA molecule that condenses during cell division. Most human cells contain 46 chromosomes but sex cells only contain 23 chromosomes.

Question 10

What is crossing over?

Answer 10

The swapping of genes between chromosomes in a homologous pair. Crossing over only occurs in meiosis, during prophase I. It increases the genetic variety of the sex cells produced.

Question 11

What is cytosine?

Answer 11

The base that combines with guanine to form a base pair. Cytosine is one of the four letters that make up the genetic code in humans and other living things.

Question 12

What is a daughter cell?

Answer 12

Any new cell formed by cell division. Each daughter cell has its own nucleus and set of DNA.

Question 13

What is DNA?

Answer 13

A molecule that contains genetic information. DNA, or deoxyribonucleic acid, is a very large molecule that contains instructions for building proteins.

Question 14

What is a dominant allele?

Answer 14

A version of a gene that is expressed even when only one copy is present. A dominant allele is represented by an uppercase letter. Yy or YY will result in the appearance of the Y trait.

Question 15

What is a dominant trait?

Answer 15

A feature that appears when at least one allele is present. Dominant traits include freckles, dimples and the ability to roll your tongue.

Question 16

What is a double helix?

Answer 16

A structure consisting of two chains twisted around each other. The DNA molecule has a double helix structure. The ‘rungs’ connecting the two chains are base pairs.

Question 17

What is fertilization?

Answer 17

The joining of an egg and a sperm to form a new organism. Fertilization combines DNA from the mother and father so the child gets half of its chromosomes from each parent.

Question 18

What is a gene?

Answer 18

A unit of genetic information. A gene is a section of a DNA molecule that provides instructions for building a specific protein.

Question 19

What is a generation?

Answer 19

Members of a family that are born and live at about the same time. Traits are passed down from one generation to the next by the transfer of DNA from parents to children.

Question 20

What is a genotype?

Answer 20

A pair of alleles that influence the appearance of a particular trait. A genotype is represented by two letters. An organism’s genotype determines which traits it acquires – its phenotype.

Question 21

What is guanine?

Answer 21

The base that combines with cytosine to form a base pair. Guanine is one of the four letters that make up the genetic code in humans and other living things.

Question 22

What is heterozygous?

Answer 22

A genotype in which the two alleles are different. A heterozygous genotype consists of one dominant allele and one recessive allele – Yy.

Question 23

What is a homologous pair?

Answer 23

Two chromosomes that contain versions of the same genes. One chromosome in a homologous pair is inherited from the mother and the other from the father.

Question 24

What is homozygous?

Answer 24

A genotype in which the two alleles are the same. A homozygous genotype consists of either two dominant alleles – YY – or two recessive alleles – yy.

Question 25

What is inheritance?

Answer 25

The passing down of traits via genes from one generation to the next. The inheritance of traits via sexual reproduction explains family resemblances.

Question 26

What is interphase?

Answer 26

The stage of the cell cycle in which a cell grows and copies its DNA. Interphase covers most of a cell's life span, while it is growing and performing its normal function in the body.

Question 27

What is meiosis?

Answer 27

A type of cell division that produces sex cells for reproduction. Meiosis produces egg and sperm cells. One cell divides into four sex cells by two cycles of cell division.

Question 28

What is metaphase?

Answer 28

A stage of cell division in which the chromosomes line up. Metaphase is when the chromosomes line up in the middle of the cell.

Question 29

What is mitosis?

Answer 29

A type of cell division that produces cells for growth and repair. Mitosis continues from birth to death, producing new cells to allow an organism to grow and stay healthy.

Question 30

What is a mutation?

Answer 30

A permanent change in the sequence of bases that make up a gene. Some mutations are harmless while others cause disease. Mutations can be inherited by offspring.

Question 31

What is a parent cell?

Answer 31

Any cell that divides to form new cells. A parent cell needs to copy its DNA before dividing so that it can be passed down to its daughter cells.

Question 32

What is a pedigree?

Answer 32

A family tree that shows how a trait is passed down through generations. In a pedigree, filled symbols show the presence of a trait and open symbols show its absence.

Question 33

What is a phenotype?

Answer 33

The collection of traits observable in an organism. A phenotype includes traits such as tall, purple flowers and yellow seeds. It is determined by the organism's genotype.

Question 34

What is prophase?

Answer 34

A stage of cell division in which the chromosomes condense. Prophase is when the cell prepares to divide. The chromosomes condense and the nucleus starts to break down.

Question 35

What is a protein?

Answer 35

A large molecule made up of amino acids. Proteins form structures and perform functions in an organism. DNA contains instructions for building proteins.

Question 36

What is a recessive allele?

Answer 36

A version of a gene that is only expressed when two copies are present. A recessive allele is represented by a lowercase letter. Only yy will result in the appearance of the y trait.

Question 37

What is a recessive trait?

Answer 37

A feature that only appears when two alleles are present. Recessive traits include cleft chins, attached earlobes and hitchhiker's thumbs.

Question 38

What is a sex chromosome?

Answer 38

A chromosome that helps determine an organism's gender. Sex chromosomes come in two types: X or Y. Most females have two X chromosomes while most males have an X and a Y.

Question 39

What is simple inheritance?

Answer 39

When the appearance of a trait is controlled by a single gene. Many traits are influenced by lots of genes but some, like albinism, are controlled by single genes.

Question 40

What is telophase?

Answer 40

A stage of cell division in which two nuclei form. Telophase is when two new nuclei form, each with its own set of DNA.

Question 41

What is thymine?

Answer 41

The base that combines with adenine to form a base pair. Thymine is one of the four letters that make up the genetic code in humans and other living things.

Question 42

What is a trait?

Answer 42

A feature of an organism. Traits include height, hair colour, skin colour and freckles.