diff --git a/alyx/subjects/admin.py b/alyx/subjects/admin.py
index 6febd819..40b7125b 100755
--- a/alyx/subjects/admin.py
+++ b/alyx/subjects/admin.py
@@ -126,16 +126,26 @@ def lookups(self, request, model_admin):
             (None, 'All'),
             ('p', 'All positive'),
             ('h', 'All homo'),
+            ('n', 'All negative'),
+            ('e', 'All het')
         )
 
     def queryset(self, request, queryset):
         if self.value() is None:
             return queryset.all()
-        elif self.value() in ('p', 'h'):
+        elif self.value() in ('p', 'h', 'n', 'e'):
             # Only keep subjects with a non-null geontype.
             queryset = queryset.filter(genotype__isnull=False).distinct()
-            # Exclude subjects that have a specific zygosity/
-            d = dict(zygosity=0) if self.value() == 'p' else dict(zygosity__in=(0, 1, 3))
+            # Exclude subjects that have a specific zygosity
+            # See alyx/alyx/subjects/models.py - ZYGOSITY_TYPES for explanation
+            if self.value() == 'p':
+                d = dict(zygosity=0)
+            elif self.value() == 'h':
+                d = dict(zygosity__in=(0, 1, 3))
+            elif self.value() == 'n':
+                d = dict(zygosity__in=(1, 2, 3))
+            else:
+                d = dict(zygosity__in=(0, 2, 3))
             nids = set([z.subject.id.hex for z in Zygosity.objects.filter(**d)])
             return queryset.exclude(pk__in=nids)
 
diff --git a/requirements_frozen.txt b/requirements_frozen.txt
index c7154991..dc28731a 100644
--- a/requirements_frozen.txt
+++ b/requirements_frozen.txt
@@ -1,12 +1,12 @@
 asgiref==3.7.2
 backports.zoneinfo==0.2.1
-boto3==1.33.4
-botocore==1.33.4
+boto3==1.33.8
+botocore==1.33.8
 certifi==2023.11.17
 cffi==1.16.0
 charset-normalizer==3.3.2
 click==8.1.7
-colorlog==6.7.0
+colorlog==6.8.0
 contourpy==1.1.1
 coreapi==2.3.3
 coreschema==0.0.4
@@ -14,7 +14,7 @@ coverage==6.5.0
 coveralls==3.3.1
 cryptography==41.0.7
 cycler==0.12.1
-Django==4.2.7
+Django==4.2.8
 django-admin-list-filter-dropdown==1.0.3
 django-admin-rangefilter==0.11.2
 django-autocomplete-light==3.9.7
@@ -33,12 +33,12 @@ docopt==0.6.2
 docutils==0.20.1
 drfdocs==0.0.11
 flake8==6.1.0
-fonttools==4.45.1
+fonttools==4.46.0
 globus-cli==3.19.0
 globus-sdk==3.30.0
 iblutil==1.7.1
 idna==3.6
-importlib-metadata==6.8.0
+importlib-metadata==7.0.0
 importlib-resources==6.1.1
 itypes==1.2.0
 Jinja2==3.1.2