Name _________________________
Heredity – Cloze
Directions: Choose the correct words from the word bank below each paragraph to fill in the blanks so that the
sentences make sense.
DNA (_____________________ acid) is known as the building _____________ of life. DNA is the link
between parents and _________________, as generations of organisms pass down their hereditary information
to their children. The ________________ of DNA is known as the double helix and was discovered in the 1953
work of scientists Watson and _______________. The function of DNA is to make __________________
molecules for the body. Much of the body is made of protein including our hair and __________. DNA is unique
in organisms in that it has the ability to _______________, or make copies of itself.
offspring
Crick
protein
replicate
nails
structure
block
deoxyribonucleic
DNA is made up of four different molecules called nitrogenous _______________. The four bases are
called adenine, guanine, cytosine, and __________________. There are _____________ to the way that these
bases pair up with each other to form the double helix. Adenine will always pair with thymine and guanine will
always pair with ___________________. At times, the DNA molecule, which can be made up of very long
strands, will need to be cut at a ________________ place. When a portion of DNA needs to be cut in a specific
place, the molecule that will do the job is known as a __________________. An enzyme is an important
chemical in the body that helps to either break down or put _________________ molecules for important body
processes.
thymine
specific
enzyme
together
cytosine
rules
bases
Smaller sections of DNA make up what we call _____________ that will control certain traits. A
_______________ is a characteristic that is expressed in an organism. An __________________ of a trait is hair
color or eye color. Groups of genes come together to form ____________________. Human beings have ____
chromosomes in each body cell; humans have ____ chromosomes in their sex cells. When the sperm and egg
meet during reproduction, this process is called ________________________.
example
23
chromosomes
fertilization
46
genes
trait
1
Sexually reproducing organisms have an advantage over ___________________ reproducing organisms
because their offspring will benefit from genetic ____________________. Sexually reproducing organisms use
the process of _________________ to create sex cells; this is a cell division process. Asexual organisms must
use the process of ______________ to reproduce. Asexual organisms have offspring that are genetically
__________________ to the parent.
meiosis
variety
asexually
mitosis
identical
When genes are ___________________ in organisms, there are some basic rules that are observed.
Some sections of DNA are more “powerful” than others and are called ________________ because they always
express themselves over the “weaker” or less powerful genes that are called ________________. A
__________________ square is a tool that is used to determine the probability or _________________ that a
certain trait (dominant or recessive) will be expressed in an organism. In reality, all traits are not ruled
completely by dominant and recessive behaviors but there can be a mix of the two. When gene expression is
not completely dominant or recessive but instead it is mixed, this phenomenon can be called
__________________ or ___________________ dominance
chances
co‐dominance
incomplete
recessive
Punnett
dominant
expressed
2
Teacher Answer Key (all of the words that fill in each blank are listed in order for each paragraph)
Paragraph 1: deoxyribonucleic
nails
blocks
offspring
structure
Crick
protein
replicate
Paragraph 2: bases
thymine
Paragraph 3: genes
trait
rules
cytosine
specific
enzyme
46
23
together
example
chromosome
fertilization
Paragraph 4: asexually
variety
meiosis
mitosis
identical
Paragraph 5: expressed
dominant
recessive
Punnett
chances
co‐dominance
incomplete
3