STEM Summative

alleles

different forms of genes for a single trait

dominant allele

one whose trait always shows up in the organism when the allele is present; always expressed

recessive allele

one whose trait is hidden whenever the other allele is present; only expressed in the homozygous state

heterozygous

genotypes made of two different alleles

homozygous

genotypes made of the same alleles

heredity

the passing of physical characteristics from parent to offspring

genetics

the scientific study of heredity

trait

each specific characteristic, such as stem height or seed

gene

used to describe the factors that control a trait; section of DNA molecule that contains information to code for one specific protein

purebread

the offspring of many generations that have the same form of a trait

hybrid

an organism that has two different alleles for a trait

fertilization

a process in which new organism begins to form when egg and sperm cells join together

genotype

an organism’s genetic makeup, or allelles

phenotype

an organism’s physical appearance, or visible traits; how a trait looks or is expressed

Punnett square

a chart that shows all of the possible ways that alleles can combine in a genetic cross

probability

a number that describes how likely it is that an event will occur

incomplete dominance

occurs when one allele is only partially dominant

example of incomplete dominance

codominance

occurs when both alleles for a gene are expressed equally

example of codominance

multiple alleles

three or more possible alleles determine the trait

example of multiple alleles

eye color

polygenic inheritance

occurs when more than one gene affects a trait

example of polygenic inheritance

height

nitrogen bases

molecules that contain nitrogen and other elements

What are the four nitrogen bases?

adenine, thymine, guanine, cytosine

how nitrogen bases mix

A goes with T; C goes with G

What does DNA stand for?

deoxyribonucleic acid

DNA replication

the process in which an identical copy of a DNA strand is formed for a new cell; because of the way the nitrogen bases pair up, the order of the bases in each new DNA strand exactly matches up the order in the original DNA strand

orders of structures (smallest to biggest)

nitrogen bases, DNA, chromosomes, cell

good path of cell division

makes an identical copy

bad path of cell division

leads to mutations (change in cell) which can cause cancer

What did Mendel observe?

the offspring of the F1 generation were always tall and the offspring of the F2 generation always had the recessive trait a quarter of the time

significance of Mendel’s observations

showed that the offspring traits are determined by individual, separate alleles inherited from each parent

What are DNA strands connected by?

nitrogen bases

Where are chromosomes found?

the nucleus of a cell

What is DNA made of?

strands are made of deoxyrybo sugar separated by phosphate; rows are made of the nitrogen bases

What are chromosomes made of?

genes

sequence for ATCGGC

TAGCCG

What genetic structure allows genes to pass from parents to offspring?

chromosomes

Where does the male’s genotype go on a Punnett square?

the top

Where does the female’s genotype go on a Punnett square?

the left side