Y9 Biology - DNA

Chromosome (coiled…)

coiled thread of DNA found in the nucleus ;

Genes (sections…)

sections of DNA that code for proteins and control characteristics ;

Chromosome pairs

humans have 23 pairs (46 total) ;

Somatic cells

body cells containing chromosome pairs ;

Gametes

sex cells with 23 single chromosomes

Cell cycle (series …)

series of stages a cell goes through to divide ;

Interphase (grows)

cell grows, organelles replicate, DNA duplicates ;

DNA replication

forms X‑shaped chromosomes with sister chromatids ;

Prophase (…condense…down)

chromosomes condense, nuclear envelope breaks down ;

Metaphase

chromosomes line up in the middle ;

Anaphase (…poles)

sister chromatids pulled to opposite poles ;

Telophase

new nuclei form around chromosomes ;

Mitosis

division of the nucleus ;

Cytokinesis

cytoplasm divides forming two identical daughter cells ;

Purpose of mitosis

growth, repair, replacement

Stem cell

undifferentiated cell that can specialise ;

Embryonic stem cell(can form most…)

can form most types of human cells ;

Adult stem cell

limited types (e.g., blood cells) ;

Meristem stem cell

plant stem cell that can form any plant cell ;

Differentiation

process where a stem cell becomes specialised ;

Therapeutic cloning (…rejection)

embryo with patient’s DNA to avoid rejection ;

Stem cell risks

possible viral infection transfer ;

Ethical issues

concerns about using human embryos ;

Plant cloning

produces identical plants quickly and cheaply

DNA (double..polymer…helix)

double‑stranded polymer forming a double helix ;

Nucleotide (x+y+z)

phosphate + deoxyribose sugar + base ;

Phosphate group

part of nucleotide backbone ;

Deoxyribose (Pentagon…in DNA)

pentagon‑shaped sugar in DNA ;

Bases

A, T, C, G ;

Adenine

pairs with thymine ;

Thymine

pairs with adenine ;

Cytosine

pairs with guanine ;

Guanine

pairs with cytosine ;

Hydrogen bonds

weak bonds holding base pairs together;

Gene

small section of DNA coding for a protein ;

Genome

entire set of DNA in an organism ;

Protein synthesis

DNA sequence determines amino acid order ;

Mutation (…base sequence)

change in DNA base sequence ;

Mutation effect (may…function)

may change protein shape and function